I have always been suspicious of the rear springs on my coupe. They have ten leaves are are pretty stiff. The number stamped on the shortest leaf is 665650. Can anyone cross reference this number and tell what they are from. It is not the part number in the 36 parts book. Thanks!

Replace them with some Posies springs for a better ride.
R.

I can't tell you what your part number is for, but I can tell you the original springs under a 36 Plymouth is a pretty high stack of leafs that was originally wrapped with tin. The springs were suppose to be greased from time to time, which wasn't usually done. This resulted in spring leafs breaking at the center bolt. If it was repaired before the main leaf broke, they would stack replacement leafs under the main, often adding a couple extra leafs to the spring pack. Unfortunately, a lot of time has passed since 1936, the number you see on the bottom of the leaf could be a part number for a replacement leaf, or a replacement complete spring from any of many different sources over the years.

The 2nd poster suggested a Posies replacement spring. Posies made a replacement spring with a Teflon liner between the leafs that made a dramatic improvement over the original springs, but you will have to Google their website to get the part number. Gene

I could have answered the question like this:
It doesn't matter what the springs are or should have been. You say they are too stiff. Many times this stiffness is from interleaf friction. Posies has developed leaf springs that can support your load but have a more supple ride, by putting Teflon or something like that pucks at the outer ends of the leaves. I don't think they ever just used Teflon liners between the leaves. But however they did it, their leaf springs work better than stock or whatever cobbled mess is under the back of your 76-year-old car.

R.

PS: I have a cousin with a '36 barn find 4-door Plymouth sedan, humpback trunk. It is very tempting to trade him on of my POS cars for it. Keep us posted on your progress.