340 or 383 for 1968 Dart

Just got home guys...lots of super responses! I screwed up and should have mentioned the gentleman actually has a 68 340 GTS, but the original 340 is gone. He has a 383 with the correct 383 K frame, motor mounts, exhaust manifolds and rebuilt big block rad! Also has a '70 340 with hi flow manifolds and correct rebuilt 340 rad.
A tough decision for sure. I think the 383 with the correct pieces may edge out the 340?

All the correct 383 parts you mentioned are worth a lot of money and are very rare. Is there a price difference between the 2 set-ups? The 340 would be the easiest, but I do love my 383 car and it is an automatic. It was a daily driver for years. I have had both engines in an A-Body, and I would pick the 383. I have to laugh when people say a 383 is a dog. It was a highly factored engine in NHRA stock class. The heads and cam are the same as a HP 440, so if I swap the HP 440 AVS onto the 383 what is the difference in horsepower? Not much. I knew a lot of 383 roadrunners that could beat 440's. As for handling and braking, they were plenty good, no need to reinvent the wheel for little or no gain. My factory 383 car came with .89 torsion bars and a .94 front sway bar. The only thing I swapped were 10 in drums for K-H front discs and the 14 x 5.5 wheels for 15 x 7 Rallyes.