What trans should I run?

You're better off piecing it together, a 68 318 Dart 833 has a small 904 sized output shaft and a 9.5" clutch, the bell/flywheel is specific to a 67-68 273/318 A body, the pedals also have plastic bushings instead of metal bearings like a 340/383 car.

The Z bar and clutch linkage pieces would be worth grabbing but everything else isn't anything special.