Rebuild 904 or swap for 727?

Personal experience:
A built 904 will serve you well. I would stick with the 904 (A999's are even better if you can find them).
I lucked out and found an A999 out of a old police cruiser (88' Diplomat) in the junkyard.
Put in kolene steels, red eagle clutches and kevlar bands.
I also converted it to non-lockup (which I regret, see below). And put a Cheetah stage 2 valve body from Turbo-Action.
Total cost for was about $1200, HOWEVER that is because I did most of the work myself with an 30+ yr trans tech helping me out.
I have almost 50,000 daily driven miles on this trans behind a fairly beefed up 360.
We're both even confident that it'll survive easily behind the 408 stroker I'm building.
My only advice is: If it's a street car stick with the lock-up and just shell out the clams for a good LU torque converter and level 2 valve body kit. I kinda wished I did, the 200-250 lower rpm on the freeway would've been great.