Need drivetrain input on a 68 Dart project

Don't use the hemi it will be pig unless you put lots of $ into it. There is nothing worse for our Mopar cause that a slow hemi.

Like Longgone says, if you are going to make a GTS clone use the 340. If you want a play car that will be the fastest with the least amount of effort then use the 440.
340's and the 331,354,392 hemis are getting harder to find and will do nothing but go up in value if you keep them in dry storage. The Rat Rod crowd whats those old hemis pretty bad. If you found the right buyer you could fund most of you project with the hemi sale.

Chuck