Three on the tree to auto

Want to swap my three on the tree to an automatic. 1965 Valiant, 170 slant. I've been told that I'll have to swap the crankshaft as well because "you can't put an auto behind a slant that's had a manual behind it".... I really wanna call bullsh*t on that, but thought I'd ask the experts around here.

I've got the crossmember, the trans (904), the trans tunnel out of an automatic car, the Hurst shifter from a '65 Barracuda, linkage and all the rest.

So, what's the deal on swapping?

Wayno