what kind of power is a 23 spline 833 good for?

Buddy of mine is running a 498 hp 505 tq shady dell 408 in his duster w a center force df clutch. He launches it at 3500 and hasn't had tranny problems yet after 3 yrs. I'll prob only hit the track once or twice a yr at the Mopar fests. He has snapped axles and broken pinions off of his 489/742 cases w 4:56 gears and 29" M/T street radials. I "plan" on driving easier than he does. Was going to go auto for better 60" and consistency, but its mostly a street car and I like 4 gears. I'm running less gear and less tire so I'm thinking I'll be OK. Got couple spare trannys so I think I'll go for it. What the hell, why not? 255/60/15s and 3:91s already upgraded to Moser axles years ago. I'm thinking 3rd member will break before the tranny.