I appreciate the response. I've been told that the 904 cannot tolerate the power of a hefty V8 without damage and to look for a 727. But the 727 is heavier and as you pointed out, more weight in the rotating mass. I will patiently look for a 998 for an upgrade, but I feel the 904 should do just fine if I don't get crazy.
Years ago I took a 69 Plymouth Barracuda with a 318 out and with encouragement from some friends really abused it. It had a 904 transmission. We'd put it in neutral, floor it, then drop it into reverse at full throttle. Then while it was smoking the tires in reverse we'd drop it into 'D' while still at full throttle. It would still have momentum in reverse as the wheels began smoking forward. Once it caught some traction it literally would leave rubber marks for more than one block with no gap when it shifted gears. We did this a lot and nothing ever happened to that transmission. So you can imagine my amazement when someone tells me, 'That 904 won't hold up well.'
I usually say, 'Really?' But I'm sure with a beefy 401 behind it and a stall converter with great traction it could break so I'll look for better 998 parts. Appreciate the info guys!