I am building my firstcar. 38 buickcoupe,70 455 stage 1, 700-4r, 12 bolt built for 68 olds . My front suspension is 80 camaro clip, which I just finished welding in place. I am now starting on the rear. I am using the origional coil springs and new origional shocks ,adjustable top control arms,late model stock lower control arms and a panard bar. I moved the rear back 1" to center in WW. My question is- are you better off to have the springs as far outboard as possible? I have lowered the car 31/2" and I will have to move the top of the spring to the top of the frame.. I am going to use a piece of 6" pipe to "c" the frame . I am trying to decide weather I should cut and fit all the way out to the outside of the frame leaving the outside skin or go in to the center seam of the boxed area,about 1 1/2" in, with my outside edge of the "c" to make my spring tower. Any help or advice would be appreciated. Tjhanks,Ken

You should be able to mount the springs inside the frame rails with no problems. If you want, use a rear sway bar which should keep any body roll to a minimum.

The springs(and shocks and sway bar links) should be as far outboard as possable. If you move the springs in(as in a pro street car) you need to go up on the rate of the springs (the shocks also need to valved diff)Thats one of the reasons pro street cars dont handle very well(that and big wide tires that are usally run to soft LOL) I do know what your talkin about as i am in the middle of a 39 myself.Think we are gonna use a 90 supercoupe IRS this time.

Hey 455Ken,

Sorry about the mis-fire reply...hit the wrong button, but as I was gonna say before my brain disengaged from my fingers, I can suggest a viable option the the set up you are considering. I have a '40 Buick coupe which had coil springs originally, and I used a TCI rear suspension relocator kit for a 55-57 Chevy and converted to leaf springs. I did this mainly because the person before me had used a Nova rearend and leaf springs, and I didn't have a clue what the coil spring set up consisted of. The Nova was a monoleaf spring on each side. It was not enough for the weight of my car and really didn't work that well. The TCI kit has 5 springs on each side, and is almost the same length as the Nova springs, and is adjustable front and back to set your car where you want it. Your frame may be different, but the length of the leaves had to be something like 54" to work on my frame. Chassis Engineering and other spring selling folks didn't have anything that long, all were about 48". There are probably other manufacturers that sell something that would work, but the TCI kit has basically everything you will need to make it happen. If you are interested in more detail, I gotta mouth full and plenty of digital pics to back it up.

Hey Guys , Thanks for the input but I just bought a Jag rear- anybody have any experiance at installing one?

Its a handfull on that frame. Also big bucks to fix anything.Rotors are very hard to change unless you fab up your own cradle .The e-brakes sometimes are not the best in the world if the rotors are not perfect. They still bring good money as some guys still have to have them.My vote sell it and buy a vette rear if you have to have IRS.84-90's i only pay 450-650 for complete(no miles /low miles) .That way you can go right down to you parts store and get any part. I am trying the T-bird IRS this week in a buick to see how good they will work out.They are dirt cheap so far.I know they ride real good.(own a supercoupe with a factory one,same as a mark 7) Before you get to crazy with the Jag maybe sell it and make a proffit??? I know guys will tell you how good they are ,but it was our only really good IRS choice 10-20 years ago.Now ......would try to go something diff just cause of what everything costs plus not much aftermarket stuff that works very good(rotors and pads and calip have been pretty bad aftermarket WHEN you can get them) Hey good luck keep use posted.
Maybe i will post some pix of the t-bird in the buick next week if i get it done.(they take all the 8.8 stang stuff,gears and posi and stuff)

how about using ford 1/2 ton springs? I believe these springs are 57", and I'm assuming the longer the springs the smoother the ride?