Can I use a 67 904 on a 72 225 or is the crankshaft register hole size a problem?

I've opened this discussion up on a "wanted" thread (because I may need a new flexplate) but I thought I'd post it here also. I'd appreciate any advice from people who have done it!

I have a rebuilt 904 from a 67 slant (I think it's a 170). I need to put it on my 72 225.

I've been reading about the change in register hole sizes from 67-68 and most people say that you can't put a newer trans on the OLDER motor..How about the other way around?

Also, does the register hole size affect the flexplate? Will the 67 flexplate work on the 72 crank or do I need a post 68 flexplate?

Again, thanks for the advice! I want to have my ducks in a row before I pull it apart!
Greg