Hey, Alittle1, I have a bunch of questions for you. If you can reply with some specifics, I would really be grateful.
What make and model rear end did you use?
Did you have to modify the axle width or did you go with a stock dimension?
Does it have disk or drum brakes?
Is it set up for 2.50" leaf springs or did you reuse the original 1.75" leaf springs and spring perches?
Did you tub the body or are you using typical street tires inside the original fender wells?
Are you using a rear sway bar?
How much clearance do you have between the top of the axle tube and the frame?
Are you using axle bumpers between the frame and the axle?
If you were to build another 37 Plymouth, what would you do differently on the rear axle setup?