Im wondering if anybody out there has subframed an old plymouth, and if they have what was the subframe out of?
I have a 72 Nova subframe under mine, but had to get the fatman narrowed a-arms to get the width right. there are some good disc brake conversions for these old Plymouths out there which might be something for you to consider.
Depending on what you plan to do with the car the stock set-up isn't so bad. Add disc brakes (www.rustyhope.com) and remount the shocks and save a pile of time and money. Making mounts for all of the stock sheetmetal/bumpers is time consuming so if you really don't need to... Even if you plan a v-8 swap you can keep the stock front end. .