Not to harp on the subject, but it is not frame width that is the big deal. It is track width. You can always spot an old truck on a later model full size frame because the wheels stick out too far. Even if you have a wheel with all the offset to the inside, it will look strange. Not trying to be critical, but check your track width, especially on that full size truck compared to mid size.

I have 15x4 skinnies for the front. Still probably too wide a track width? We quickly measured 3"-4" difference in cab widths 1960 to 1981. I;m guessing we need to take a more accurate measurement then..? Do you have pics of your truck that shows tire to fender clearance?

if you are hung up on the 4x4 setups and the fullsize dodge stuff is too full---there is always the 70's 80's wagoneer and scout traveler chassis----other than that there is the s10 or toyota setups------if there is a possibility of running 2wd i have seen numerous old fords from 1959 up put on a crown vic frame and chassis----i dont think the old fords were appreciably wider than the old dodges....or it might be easier to find the original frame and just weld on the frame brackets to mount the axles that fit......

No 4x4ing. 2wd and 15x4 skinnies up front.....

well if you want an older mopar setup there are full frame (no unibody) on imperials and other older than 1961 mopars--there are 2 wheel durango and dakotas---also there are 2 wheel toyota and 2 wheel s10 setups used by hot rod and rat rod builders----you probably can google up some builds on your computer.....

type in "1958 dodge d100 navy truck" it will show you pictures and give the story....its on a 2 wheel dakota frame....

This is what I "WANT" to try......

The track width of a frame/suspension is based on the width of the wheel mounting surface, and the wheel backspacing. It is measured at the center of the tire.

Lets say the wheel mounting surface to wheel mounting surface is 62" wide, and the standard wheels have the wheel mounting surface centered on the rim. The wheel track will be 62" wide.

Using the same frame/suspension that is 62" wheel mounting surface to wheel mounting surface, the "new" wheels have the mounting surface with a more shallow backspacing (the hub sits in on the rim, compared to the standard wheels above) of 1" per wheel (same width wheel). The new track width is now 64".

Using the same frame/suspension that is 62" wide, and now using wheels with a larger backspacing (the hub sits out farther on the rim) of 1" per wheel (same width wheel), the wheel track is now 60".

The track width and wheel width will determine how the tire sits in the fender. A frame/suspension with a more narrow hub to hub measurement can make a huge difference in how a tire fits in the fenders.

A first generation Dakota has a wheel track 2" more narrow then a full size Dodge truck. The Crown Vic mentioned above is 2" wider then the full size Dodge truck, and an S10 is about 2" more narrow then a 1st gen Dakota.
Gene

Thanks Gene.
I have 15x4 with 1 3/4" backspacing intended for the front. I think they might tuck in but I might go a Dakota front clip now as I'm thinking (not positive) it's a rack and pinion front end....? I have to cut the frame in any case.... or maybe just use a Dakota frame and adapt the 81 box..? We are looking for a Dakota to size up and will see what we think is best.

I want to sink the engine back a bit whatever we do, and with the Dakota there might be a possibilty of a 4 speed auto? I'm looking to have a 325/50/15 drag radial truck with a healthy small block I have that might be able to actually go high speeds and corner...

2 wheel drive Dakota are all rack & pinion steering, 1st gen (1988-1996) 4x4 were steering box yet.
A Dakota has a pretty radical kick up over the rear axle, if you use a 1st gen Dakota, you will have to raise the box floor up about 6". Still works, but leaves you a pretty shallow box if you should want to haul stuff.

Another option could be a Durango, same basic front frame under an SUV body probably has a lot less kick up over the rear axle. Rusted body Durango's are cheap. Lots of V8 Durangos, 4.7 (I'd stay away from a 4.7), 5.2, 5.9 and newer 5.7 Hemi motor choices.

I believe the newer Dakota's have a wider track then the 1st Gen, but I'm not sure when the track got wider. I have mostly dealt with 88-96 Dakotas and dabbled with a few 97-2000.

You could buy an RT Dakota with a 5.9 Magnum, and they could be made to corner pretty well, but hot with 15" x 4" front wheels though. About 2004 you could get a 5.7 Hemi in a Durango, Put that under that 60 cab and have some fun. There is a Rat Rod site i visit where a guy put a 50 something International on a 2004 Hemi Durango chassis that had a pretty detailed wright up. Gene