How much power will a stock 904 handle

Shift kit, deep pan and aux cooler will go a long way towards making a stock 904 last. The one in my Duster is a bit of a mystery, rebuilt with supposedly some upgraded hard parts but the guy I bought it from circa 2010 didn't know much about the details. FWIW I put about 35k miles on it behind a 300 hp 360, about 10k miles behind its current 360 at high altitude (~370 hp) then another 3k or so since moving to near sea level (~450 hp) about a year ago. I put a lightly-modified stock late-70s valve body in it when the original one cracked a few years back, once the power and torque jumped up from the altitude change I felt like the 2-3 shift couldn't keep up so I did a TransGo TF-2 kit on mostly "max" settings, works great now. Full rebuild would of course be ideal but I just need it to hold up until I have the funds for a TKX 5-speed swap.