The lid handle needs to be moved and D nuts installed so the cost of body work and finding the right paint. I guess the hole could be plugged. The curved inner panel will have to be painted along with the rumble seat riser re-enforcements. What is prep going to cost you, some guys can get it done cheap others pay a lot.
You need the rumble hinges. If it is an original lid then you need to find original hinges as the repros do not fit. Well the repro could be made to fit, but why? The originals fit in right and will just work. You will have to fight to get repro hinges to fit.
You will need seats and covering, rumble latch if 30-31, rumble latch catch, curved inner panel, the top shim things, rumble stops and braces, rubber bumpers, and side panels. These are all new from a catalog so you can get the price from your supplier.
Rumble seats
There are some variations depending on:
Year- some differences in lid and where things go.
Is there a repro lower rear panel- they are just built strange and will cause problems because they do not have the internal structure for a rear spare tire mount.
Is there a repro rumble lid or has it had a lot of repairs done on it?
Is the opening between the rumble lid and the lid even- the rumble lid works different with the hinge and if it is tight it might rub opening the rumble lid.
Anyway, just a few thoughts to get an idea.
You will also find an article on converting to a rumble with a complete parts list in the service bulletins.