A good TC from Goerends, the 900/400 is not too bad at all and puts the power thru without a lot of pull on the brakes, a shift kit and the typical upgrade stuff like band strut, anchor and accumulator. If you are going to use it hard then a rebuild with Raybestos HE clutches at some point would be in the works. If you are doing a lot of slow heavy work remove the check ball in cooler output line and add an external cooler with a fan.
That would be my choices along with some 18" rims and good MT tires.