With 450HP - how much torque? - in a sub-3000-lb car, the 904 will work with good clutches & bands. I'll assume no transbrake. The 727 is stronger, takes a little more HP to drive, which may amount to .1-ish ET. That said, if you get greedy and plan on 600HP or a transbrake, the 904 will need a little more aftermarket help than an equivalent 727. My basically stock 904 held up well until I put more than 600HP to it in a low-10s 3000-lb SB Duster; after that a mid-range CRT 904 was necessary. (6000 stall, footbrake car.)
Call John @ CRT - he's a member here - and tell him your combo & goals; he'll treat you right.