yes its a good setup... your gonna feel less power with the th400,, if i remember some estimated about 10-15 horses less.
but if you keep fluid in the tranny, and keep it cool.. it is the one to have if your gonna run an auto.... Furthermore, when you go to a doubler, you already have the right spline count on the input shaft.
obviously your also gonna need a way to shift it... id go out and get you the B&M light truck ratchet shifter