Use an aftermarket cable operated auto trans floor shifter to shift your th350. ( B&M, Hurst)
You do not need to weight down the truck to get traction.
These "Caltrac" traction bars work great on any leaf spring vehicle including a S-10. Really increase the bite while controling leaf spring deflection, (wheel hop)
Get some DOT legal high traction rear tires with a sticky tread compound.
EG: BFG drag radials, Mickey Thompson Sportsman Pro or ET street Tires, or ET Street Radials.
A conventional radial tire does not give enough traction.