A body Rear in 63 Cat
 

So here’s the story:

I have a long term 63 Cat project that has changed directions over the years and is now the benefactor of many left over parts thanks to a thinning of my collection. What was going to be a minimalist bracket car with an automatic, it’s now a 455/M-20 street car. The one legger, freeway geared original rear will not do. I could certainly swap out the pumpkin and axles with something more suitable to the 4 speed, but That’s expensive. It also happens that I have a nearly new Currie 9 inch that I had built for my 68 ElCo laying dormant in my shop. The 9 inch was damn expensive, but it’s everything I could want for the Cat: 3.50 gears, traction lock, 31 spline forged axles and essentially brand new. Unlike the Pontiac rear, it has a massive aftermarket following for things like brakes and stuff. The one problem is that as it’s built for the A body, it won’t bolt in. But it is “close” in the sense that it’s a 4 link, coil spring configuration. So just how much work will it be to get it to fit? I’m about to find out.

With an afternoons work, I was able to drop out the 9.3 and stuff the 9 inch in there to evaluate the changes. It looks like it will work with some fabrication. It’s now a roller, but a ways from capable of driving. So far, I’m in for the following changes:

New lower control arms. The Cat arms work for the time being, but the angles are not quite right. New arms will have the bushings offset slightly to accommodate the slightly different width. On the plus side - the A body rear sway bar will fit
New upper arms. This is a more severe change from the Cat parts. The point where the A body arms intersect the frame is MUCH narrower than the Cat brackets. Fortunately, it will be fairly easy to add new brackets to the frame in the correct place. I don’t even have to remove the old.
New spring perch. I hoped to not modify the Ford rear, but I’m planning on airbags for springs so there will need to be a simple welded on perch. There is a chance I can get clever and fabricate a bolt on perch - we’ll see.

Anyway, I’m not attempting to convince anyone that they should modify their Cat to use an A body rear, but for me the juice is worth the squeeze. I’ll post progress as it comes (slowly) Hope some of you can get something out of it.

I love mods like this. You could make adjustable control arms from 3/4" swedged tubes, with heim joints and other various rod ends from Speedway.

https://www.speedwaymotors.com/Swedg...read,2091.html

Yep. That’s in line with my thinking. Lower arms are simple 1.75 DOM tube weldments with universal poly bushings. Upper arms are a hybrid box section at the rear, transitioning to tube and poly rod ends at the frame. The uppers are adjustable to set the pinion angle and center the rear end from side to side.

Was planning to build some offset lower control arms to pick up the stock cat frame horns. As it turns out. The stock cat brackets are actually narrower than the A body, AND they are fairly easy to remove. Drill out two rivets, cut some cheezy factory welds and apply some persuasion with a BFH and they are free. The replacements are simple angle iron. This weekend saw me build the new lower arms using some generic poly bushings. Pictures show everything fitted and the frame mounts ready to weld in place. Next step is fabrication of the upper arms and brackets. Stay tuned.

Sweet '63 Mike! Following this one. The GT-37 is supposed to be going in for body work & paint after the new year...keeping my fingers crossed!

Dennis

Thanks Dennis. Looking forward to updates from you as well.

Bit of an update... I'm in the middle of a move to Arizona and the rear end swap is on hold until I can get the new shop set up.

I made some adjustable control arms out of rock crawler joints, if it’s something you’d be interested in I can dig up the link.
Very beefy units.