Contrary to popular opinion this hunk of tin is not dead.

Still coming along Quint

I have managed to get a little further along over the past couple weeks.
I started by installing the RH frame rail from the rear front spring hanger inside the rail forward to the c/l of the kick at the base of the firewall.
These rails are installed flush at the bottom of the rear rail and ran level with the rockers.

Next I installed the LH frame rail.
I determined dimensions on these rails to be 52" long from the rear to where the front rail kicks up at the firewall.
I ended up adding an additional wood brace to the so called frame jig to establish and carry the new rails.
I also double checked both new rails for plumb left to right where they kick up below the firewall.

I began mocking up the front frame rails and determined the angle of the new rails to be 2.3 degrees.
2.3 is too small of an increment to split for a miter joint so the rails installed at the center of the car are cut square and the new front rails are cut at 2.3 degrees.
I am only mocking everything up right now as I'm trying to look eight steps ahead and see what I can do now that will help later.
I made the 2x3 cross brace to cap both front rails at the front.
After confirming the distance of 35 3/4" for the locater pins in the leaf springs on the straight axle the front frame rails are installed at 35 7/8" c/l dimension. This is actually about 2" wider than the factory rails were installed.

You find you'll have to check and double check everything you do to assure everything stays square...plumb and level.
After pulling angle dimensions on the frame at the new front sections to check square they were about 1/32" off. Not enough to worry about on a 64 13/16" length. Nice thing is if you ever have to use any of these points at the frame kick or the front to square something up they are dead on square.
I need to find a good supplier to source the leaf springs from...all of the ones that Speedway has have too long of a dimension from the locater pin to the front spring eye.

I ordered the leaf springs today.
I had a guy with one of these cars tell me a while back to use trailer springs.
I found a set of 26" springs with a 13" eye dimension.
They already have urethane bushings and the assembly bolts come with greasable zerk fittings.
I had asked a while back if anyone knew a reason not to use the leaf spring sliders on the rear of the springs rather than shackles. I've never heard anything...I guess as of now I still am planning on using the sliders.

So here is a picture of the front suspension mock up.
This is a 12" forward relocation from stock of an A-100 van axle.
With this design as indicated in the photo's there is a 7.5 degree lay back at the kingpins.
There's really no way to know how this will react once everything is loaded with weight.
I think the only thing I'm going to do different than what is pictured is to make the slider bracket at the rear so it can have shims installed between it and the frame rail that would bolt in thru a bracket welded to the frame.
If ride height is an issue I can also use a tapered spacer between the springs and the straight axle at a later time.
So far I'm happy with how easy this installed and with using the greasable bolts at the front and bearings at the sliders it should work well.

A couple more of the drivers side.
I also ordered all of the new brake components for the 10" x 2 1/2" front drums for the A-100 Van axle. I single sourced everything thru www.partsgeek.com except the bearing cover caps on the hubs.
The other pictures are of the miter at the front frame rails before they were welded and the RF box tube pad to carry the roll cage bar at the RF corner. This tubing was tied in to the side of the frame rail and then installed recessed into the inside of the rocker panels where they were plunge cut. Being 3" wide it gives me a little wiggle room later for the roll cage bar placement.

Ok, so what's the issue here, Q?

I used that leaf spring slider on the 69 Dart for a couple summers now with zero issues on the rear. Never seen or heard of anyone using it here and was just looking for some input.
As for the other thing we talked about...I'm going to keep a lid on that until I pull the trigger...IF I pull the trigger...
I mapped out an area on the front rails near where the front hangers for the springs are for a bar to tie in from the frame back to the roll cage. This will give me a good point for the shock bracket at the top.
I did a few small modifications to the front spring hangers tonight and will post pics once I get them loaded Thursday.

Here are a few pics of the modified front spring hangers.
Rather than just two tabs that stuck down I added a piece to set against the bottom of the frame and a second one to wrap down around the front of the bracket.
This keeps them solid left to right and increases the available area to weld them in.
On to the next task...floorboards...tunnel and firewall...

I had a couple nice days outside so I gathered up the fenders...doors...hood and bumper parts for the front end from storage.
I spent most of the day yesterday stripping undercoating from the fenders.
I temporarily pinned the original passenger side door on and checked all the gaps.
Everything still fits well. I was kind of worried that maybe some of the integrity had been sacrificed with everything that has been modified. I don't see any issues. I marked where the leading edge of the fender needs to align and removed the door.

The fenders I have are an accident that's already happened on numerous occasions. They were only good for what I'm using them for.
I hung the passenger fender and dimensioned for the drivers side door and hung the drivers side fender. I sat the hood on and made sure everything seems square.
Then came the only actual fun. I used the laser and located a level line and a center line for the modified wheelbase. Relocation will be 10" forward.
I installed tape on the lines that will need to be cut. The area painted in black will need to be removed. Notice how well the leading edge of the cut line aligns with the original corner of the front fender above the bumper. You can achieve this by measuring 10" forward on a level line from the wheel well and making that your cut line.

Now you can cut...
Throw away the unused piece (I'm lying..don't throw away anything that has a radius or bend in it)
Then tack whats left back together...

I everything works out you should end up with a dimension of about 10 1/8" of opening that will get new metal...Position the wheel opening tin and support it so its sitting where it would when finished and begin tacking it back into place.
Now it starting to look like something...

Axle relocation was 12''...
Fender relocation was 10"...
I couldn't resist digging the front wheel out and hanging it on to see what I have.

Then it was on to welding up the trim holes and the antenna hole. Not as much fun...but it needs done never the less...
I think I can pillage the 63 330 I just got for parts for a piece of metal to weld into the front fenders...

It worked!
The 63 330 gave it's life today...as if it wasn't dead before.
I sectioned an area out of the doors large enough to do the patch panels for the fenders on both sides.
When I cut the back door a 3/8"-7/16" craftsman wrench fell out...
I glanced down after shutting the grinder off and saw the blade was broke in half...
Dumb luck I caught it before it got painful...
Then I got to thinking...
What would happen if I cut a section out of the rockers to finish off the bottoms of the fenders...
It's worth a shot anyway...

I don't know what the #$%^!@#$ they used for undercoating inside the doors but holy crap was it ever a bear to get off
I held the patch panel in on the outside of the fender and traced what I needed for a filler...cut it and installed it...No binding no pressure it just fell right into place...
All but one small area that I had to trim with the tiny Dremel wheel...
I did manage to clean up the passenger door today and got lucky as it was still pretty solid...