The only difference in the bellhousing with any 1.6, is the newer 8v and 16v have extra support braces from the block to the bellhousung. The early 1.6 8v and 1.3 doesn't have the braces.
The tank, you can make the 4 door tank fit in a 2 door. All you have to do is remount it. You don't have to change any fuel lines on the frame. The 2 door tank is 12.5 gallons and the 4 door is 14.5 gallons. I think it would be a double benefit, the right pump and just a little bigger tank.
Just a thought, from someone that has played with the peices to do that very theory.