340 vrs 360
Depends on what you want to do with it.
If it was a real 340 car, that would probably sway me to the 340, unless you're really chasing timeslips.
Then I'd do a 360, and like abodyjoe says get a roller motor, or a 5.9 Magnum (which is roller also and you might not have to rebuild the shortblock).
Of course, I too happen to be selling a '69 disassembled 340 engine. LOL