Do I need a stall converter?

Absolutely! ALL converters stall. The real question is... at what stall RPM will your engine/chassis combo work best? The right torque converter can make a car, the wrong one can turn it into a dawg! And there is more to torque converters than just the stall speed. Namely torque multiplication and efficiency. If you are going to deviate from stock, I suggest you talk to several torque converter manufacturers and get their recommendations. Their info is free, so why not? Then you can make an intelligent decision based on your combo, intended usage and budget.