There is actually 4 pieces to the roof. The drip rail, the outer panel, the inner panel and a header panel sandwiched in between the inner and outer panels. There are about 257 very randomly placed spot welds holding the whole thing together. You can't buy any of the pieces new and most used stuff has some degree of rust. When I did the roof on my 92 I had found a pretty clean roof from a parts truck but it had some rust through right at the windshield flange. After drilling the spot welds and removing the drip rail, header panel and outer skin from the donor I had 3 pieces of swiss cheese. My inner panel was still solid. It was a PITA and I don't think I want to do another one.
As for the fuel injection that should be easy. You need to regulate the fuel pressure down or replace the pump to something carb friendly. Intake manifold, carb, distributor and ignition box should get you up and running. You may need a wire for the a/c clutch and bypass the ASD relay to get the fuel pump running but that's about it.