You've been watching Monster's Garage again haven't you...
I thought they were called suicide doors because if you opened one up on the highway at high speed, they would flip back and you could get blown out the door. (no seat belts back then)
Anyway.

* AutoLoc sells the door kits if you have to have them. Too much work I think.
* A Huge Sunroof instead of T-tops would be better. We got one for my brother in laws Monte Carlo at the junkyard off of another car for $25 and installed it.
You can't cut the top of the doors off and keep the windows from flopping around. Also cutting the roof disrupts the structural integrity of the unibody.
* V-8 in the trunk sounds like a Toronado swap. There are Corvairs on the web that have tried this, many have failed. Converse and JTR sells the V-8 (in the front) swap kits for the 240. Besides where will you put the rumble seat.
* Don't jack up the car, it's just wrong and it will handle like a Jeep.
* The trunk rumble seat idea does sound cool. If you reinforced the back end and used outdoor seats like a dunebuggy, I don't see this a problem if you had seatbelts. Remember the Suburu Brat? The third seat in a wagon places the passengers just as close to the rear bumper. Maybe a backwards folding wagon seat would be a possibility.
Ben