whats first?

Ok guys, I know the debate is out there on 904 with a 8 1/4 VS a 727 with a 8 3/4 but Im going to keep the 8 1/4 and 904.

So anyways I have a 360 with a stock 1974 904 transmission currently but I have a new http://www.summitracing.com/parts/ape-53022/overview/ TQ going in it, and the 8 1/4 has been changed out to a open end 3.21 gear set.

The question is, should I rebuild/beef up the transmission next or should I get a suregrip unit in the rear first?