904 or 727 ?

Hi all!
I'm getting to the point where I need to get my transmission beefed up for the 500 hp stroker I'm going to install.

My trans guy said I should go with a 727 as they are stronger and cost less to beef up than a 904.
He said 72 to 78 so I wouldn't get a lock up unit.

The car is a 67 Barracuda coupe. I think the 727 will fit with no problem.
Am I right in thinking this?
Any years to stay away from?

Thanks in advance for any help!

CudaMike13