LSX donor car for a 68 firebird

[firebirdzig]

I'm looking at getting a wrecked LS car. Not sure if I want to look at an LS1 or LS2. However if I get a GTO/camaro/Firebird which parts will I be able to use on my '68 firebird? I know with a different crossmember and motor mounts the motor and trans will work, but what about the rear end and the brakes on it? The front disc brakes? Fuel tank? Ect.... I understand I'll need a return fuel line to the tank and a different fuel pump, the engine wiring harness and ECU and things of that nature. Thanks for the help.