Mustangs don't use the pads, and the U-bolts are shorter. Part of the reason this setup is there is the Cougar uses a wedge to get the correct driveline angle. Offhand I don't remember which direction the wedge goes. By not using the pad, you're in effect moving the axle closer to the spring, and this could also effect the driveline angle.
Also, the pad and wedge has the same affect as using lowering blocks... removing them will raise the rear end at least an inch. You may want to get the springs with the 1 inch drop if you are going to delete the pad and wedge.
I used ESPO leafs on my Coug and kept the wedge and pad. the result of the new springs was an 1 inch lift over the old sagging springs I replaced.
FYI, installing the spring with the poly bushing was a PITA!
If you do a search back in to the old topics, search for a thread titled 'Leaf Spring Wedges'. We thoroughly discussed this topic there. I had also clown-colorized a pic of my modified rear end mounting showing the elimination of the rubber sandwich but keeping the leaf spring wedge. If you can't find the original thread, look in my photo gallery.
You really don't need to keep the rubber isolator sandwich. It is the bane of leaf springs!
They will hold water, causing rust and then spring breakage.
Eliminate the rubber and you'll have more road vibration transmitted to the rest of the car.
Eliminate the rubber and you'll have crisper handling.
Eliminate the rubber and you'll have less wheel hop on hard acceleration.
Eliminate the rubber and you'll raise the rear of the body about an inch. Use lowering blocks if you want to maintain the height you had.
There are many pros and cons either way. Me? I'm eliminating them on my cats. The choice is yours. Either way, make sure you keep the wedge plate!
BTW Royce, I've never seen a Mustang with the wedges. I've seen 69s, 70s, 71s and 73s, all without the wedges. The axle pad sits directly on the spring.
As Royce noted, new bushings are available from a number of sources. Also remember that the rear shackle bushings may not be the same as Mustang bushings. My generation Cougar springs have smaller diameter bushings than Mustangs. The rear axle mounting u-bolts will have to be longer than the Mustang bolts because of the thickness of our wedge plate.
This really intrigues me....I am currently restoring my cat. I have everything off the back end and just POR15's the underside and painted it. I am in the process of b;astiong and powder coating the rearend and parts and am in a delima about weather or not to keep the rubbers as well. I want the quiet ride but also want the handling. I did the shelby from control arm relocation, went with 1" front bar and am buying a 3/4" rear bar???? What to do, what to do???
I just looked in the Master Parts catalog and sure enough they don't. I wonder if the Cougar needs them to compensate for the longer wheelbase? The rest of the car is virtually identical to a Mustang suspension - wise excepting the additional iso - clamp on the rear springs and the length of the springs.
When I did my leafs everything went very smooth until I got to the shackles and then the trouble began.
First of all here's a tip: For about two weeks prior to replacing your leafs spray WD40 on all your old hardware every other day or so. When it came time to remove the old leafs all the hardware came apart very easily.
The article at TCCN was a big help in explaining the process too!
When you get your new hardware and bushing you will notice that the poly is considerably harder and less flexible than the rubber bushings. Having a more flexible bushing at the shackle would have made the last bit of installation a great deal easier but since the poly doesn't flex and the fit is SO tight it was a real pain to get the shackle bolt to slide thru the poly bushing (even with generous amounts of lube).
BTW, ESPO has everything you need including the rubber insulator pads.
Good luck and you know we're here to help if we can.
I am getting ready to buy new leaf springs for the m code conv. Before, for the h code, I bought them from MU because of time constraints. This time, I have the time. How does ESPO leafs compare to the others available. They are WAY less expensive than the others. Are they as good? Use poly or not? Anyone?