Any issues w/ mini-starter and different torque converters

What about slant six and big blocks?

Dunno about the big blocks, but our 1964 /6 definitely had a small converter register hole in the back of the crank so that when we ordered a converter, it had to be a bastard unit, with a front register piece sized to fit inside a small register crank-hole and have a 27 spline (large) input shaft dimension because it was going to live in a drag race environment and in that case, bigger IS better.