The front frame rails on an F body are not parallel with each other. At the point the 4 front crossmember bolts attach onto the frame rails, the front 2 bolt up mounts are 4" wider, center to center, then the rear 2 bolt up mounts are. I believe the outside dimensions at the front are 38" and at the rear bolt mount the frame is 34" outside. The frame rails are also not flat nor are they square or rectangular shape. The rails are also not uniform in size or shape from the radiator to the transmission crossmember. If your planning on hanging anything other then the factory crossmember on the rails, expect to replace the rails with tubing. If you do that, do yourself a favor and replace the transmission crossmember at the same time.

I'm going to guess the hub to hub width is close to 64" wide, it is about 4" wider then the hub to hub on the front of a Dakota frame. I junked the last F body crossmember here a week or 2 ago, so I can't measure for sure. Gene

Thanks for the info Gene, that is extremely helpful. I can do a weld-in clip from 32"-35" outside to outside width so should be able to make this work. What I'll do is cut the entire front rails out, fab some down tubes which will weld to the floor and back to the rear cross-member, similar to sub-frame connectors. Then I'll triangulate from the inner rockers to the the length-wise tubes so I won't have to worry about "splicing" in to the existing frame rails and trying to make things match up. Should work out pretty good. Once finished, I'm hoping to stuff a 10" wheel in there. Will

Engine is out. Cleaning off old Ziebart undercoating. Checked Dakota crossmember for fit. Tight, but will slide in. Requires surgery to mount.

Greg

Still more slow progress. Snails pace. F-body k-member out and trial fit of Dakota crossmember in. I think... it's gonna work. I cleaned up some of the gunk on the frame rails, marked dead center for placement and tapped it in with curses and a mallet. Tight, but fits fine. One of my major concerns was how the lower a-arm was going to clear the frame. It does. It will come out for more cleaning, marking and cutting, but, I think I'm on the right path.

Greg

Stick with me on this Poorboy.

Just want to be sure I'm understanding correctly, this Dakota set up is sitting inside the original F body "frame" rails and your going to attach to them, correct?

OR, when you cut your F body k-member out, you cut out the frame rails as well, and all I am seeing is the inner fenders for your F body?

If you are doing the 1st one, I believe your going to be OK.

If your doing the 2nd one, my concern is that you will need some sort of boxing or tubing outside the Dakota subframe. That subframe is designed to attach to the Ford "C" channel frame for support. If you cut your frame rails out, what will provide the support for the subframe? Gene

The fist one is correct. The Dakota crossmember is sitting INSIDE the F-body frame rails and will be attached to them. I'll have to cut out sections of the rails for the "top hats" but I will not be removing them. I will also be cladding the rails for support AND, adding a c-channel under the radiator for suuport. Something like this:

http://i160.photobucket.com/albums/t164/Freaks-Photos/70%20Dart/K-in-car2.jpg

That's the plan.

Greg

Looks/sounds like a solid plan.
Gene

This may not look like I've done a lot, but, I have. I've had the Dakota crossmember out then in again three times and the F-body member in and out twice taking measurements. I'd laid a long straight edge across the F-body k-frame and using the grease fittings on top of the upper ball joint, marked out the axle centerline. I had to do this multiple times to make sure I got it right. I did the same with the Dakota crossmember out of the car. Once I got it all marked out to where I thought it should be, I put the Dak one back in. Before I did that, I had to trim a piece of the frame where the drivers side rear k-frame mounting goes. Once trimmed, it slipped in with some shoving. Things I have learned. F-body frame rails are not symetric. The drivers side rail bows in slightly where the steering box coupler goes. I'll have to do something about that later. Right now, it's just sitting there (again) marked out. Fits well. No major cutting and welding done yet.

Greg

Once I got everything where I THINK it should be positioned, I stuck the spindle and brake assembly on and held it in place with tie wraps and a block of wood. I couldn't put the spring perch and upper a-arm on yet. Just checking for fit.

After that, stuck on the Mopar Rallye wheel and the fender from the rafters. Looks OK

Fits under the fender well.

Wife and kids are out ouf town for the week so I got some work done. This is "Buck". I laid 2"x4" steel retangular tubing onto the Dakota crossmember and clamped it together to get basic dimensions. I then placed the 2"x4" wooden studs on top of that assembly to duplicate the outside diameter and proper length I'll be working with. When Buck came together, it was an easy (and light) way to place it against the frame bottom and mark where I needed to cut. Buck proved that my idea might just work.

Greg

With all the marking and measuring done, I broke out the Sawzall, said one last "Hail Mary" and started to slice. Turns out, I didn't have to slice that much. Nerves of steel....

Greg

Kids, don't try this at home....

Greg

After another couple of days of laying on my back, measuring more and cutting more, I was able to get two lengths of the 2"x4" steel tubing to slide into the frame rails. I actualy had to narrow the tubing slightly to slip in. This is where I'm at so far. The two new frame rails essentially duplicate a 53 Ford F100 frame in width. Once the frame rails were in, the Dakota crossmember slipped right in. Nothing is welded up yet. I've got to take it apart and clean it up first, but, at least I've gotten this far. At the rate I'm going, it may take a while.

Greg

Those "high water marks" are where I originally thought the crossmember should be placed after measuring and marking. However, when I put the steering rack on I realized I had to lower the crossmember even more to clear the pump lines. It's right where it should be now (I think).

Greg

So this is where I'm at with this. Since I lowered the crossmember in the chassis it may cause the car to sit high. Back to Craigslist and I scored a set of Gen 1 Dakota drop spindles. I'll use them if I need them.

Greg

Greg, are we having fun yet? I think your doing a great job, this stuff isn't as easy as some people lead a guy to believe, is it?
As I understand, you are faced with lowering the MII crossmember so the tie rods would clear the tubing inside the frame rail. Now, because the lower control arms bolt to that crossmember, because you are concerned about the ride height?

Two things come to mind. 1) Since the tubing is extra reinforcing, can you put a notch in the tube, and box it back in so the tie rods clear, without lowering the crossmember? You can probably notch away almost 1/2 the vertical wall height on both sides of the tube without compromising the strength as long as the tube is not the only structure there, and you box the notch back in with at least 1/8" wall material and fully weld.
2) Another possible option is to move the mounting holes for the lower control arm higher in the crossmember, you may have to trim the crossmember for additional clearance for the control arm swing. I suggest this one because many MII setups only have 1/2 of the control arm mounted to the crossmember, and the other 1/2 is attached to the frame rail. Maybe a combination of these two options would work better, or maybe neither will work. These things are hard to figure when you can't look at the real thing. Keep at it, you will get there. Gene

LOL! You called it Gene. This is BIG fun! Sort of. :-)

Let's face it, you haven't lived until you take a look at the inside of an F-body "frame". All kinds of stuff in there I'll tell you. It's actually a bit stiffer than I thought it was. Anyway, I'll correct you on why I had to lower the crossmember. It was because the Dakota setup places the power rack and pinion slightly higher than the base of the crossmember. If you look at the pic I took, you'll see the truck rear sump oil pan has to clear the rack and lines. So, that's what threw me off in my first set of measurements. I'd originally done it without the rack. Glad I caught that. Man... this is work....

Greg