The 38 frame is a decent foundation. It already fits your body so that's a plus.

A new front suspension would make it ride better, unless you like a dump truck's ride. If you Dodge is anything like my 38 Plymouth, then a later axle will bolt in. I used a 9 1/4 from a 79 Newport.

things get a bit tight under the driver's side floor board, especially if you want to keep it a stick with the M/C in the stock location and run an exhaust pipe thru there.