how do i figure out trap rpm with my diff gear?

more than likely the bias ply M/T sportsman tread in 29x13 inch size...im worried im going to have a hard time hooking with this much gear on a street tire...gonna have slant 6 t bars up front and trying to get my hands on a set of 002/003 ss springs for the rear; i also have an adjustable snubber for it