you must be unaware of a T-400 strength.
The t-400 with very little work will support a 600 hp motor and good traction.
Proper clutch pack set up , bushings and basic rebuild technique's are all that is needed.
I ran 850 hp ( dyno verified) through a t-400 in the early 1980's. 13 inch slicks on the car , 9 inch Ford diff with 4.86 gears
Dont worry how old you are... it is the mileage on your body that adds up.