I've been in a DSM that had a 1st gear GVR4 (taller) and it broke with a clutch dump. If you want to do high RPM clutch dumps, than a shorter 1st gear might be better.
If your willing to slip the clutch, not go for aggressive dumps, than the stock transmission isn't really a weak point. The rear axles with stock suspension and hard launches might be more of a weak point than the transmission.
How you drive it is going to matter more than your HP/torque number. I don't think anything is going to break with spirited driving unless you hit a LOT of power.