You don't have that thing done yet?.....lol. Isn't that the green car with manual trans? I guess to answer your question,there is not much available. I put the 3 piece trunk pans in mine because you would have to cut the whole rear apart to correctly install a one piece. If your rear crossmember is nice where the two rear body bolts go into the frame,I think you would do yourself a favor by staying away from the one piece. You can trim the old pieces out in such a way that the seam is just above that rear brace,so in effect,good bodywork is work that no one can see that you did.
I was going to buy a deck lid from gs sizzler,but I ended up using my original after all the blasting damage was repaired. He may still have a good one. Don't be afraid to just buy the trunk pans and repair the rest. Once the pans are trimmed out of the way,you can sometimes make new pieces where the sandblaster makes holes,especially at the bottoms of the wheel houses where there will probably be some rot. The car looked pretty decent for a 50 year old. I would buy the panels first,and then cut your old ones out and trim all the caulk and old spot welds out of the way before sandblasting. Just because a new panel is a certain size doesn't mean you have to use all of it.
The scariest part of a roof is the area that the glass seals to. Remove the glass and blast this area good. Stay away from any flat surfaces with your blaster,it will warp them to death. Try to fix the roof small in areas if you can. If it is Swiss cheese when you're done,then look for a roof. The more you chop apart,the harder it is to make fit. Sometimes your local roofing and siding guy is your best asset. A good metal brake and a new piece of sheet metal can go a long way on welding repairs.
If it was easy everybody would have one,Dan