A-999 Swap and Information

The clutch plate splines looked fine. We couldn't figure out the grooves in it either. All the clutches were fried & the steels burnt & someone had sanded/ground the burnt spots. They seemed to use it as 904 w/o locking out the OD behind a 340 in a 70 Challenger. My buddy is installing the good clutches,bands & also a Trans Go shift kit if they make 1 for it. It is going behind a 0.40 340 with balanced bottom end & wondering what converter I should use.