a 13b in any situation will always have 2 rotors. a 20b has another rotor slapped on the end of it, and a 26b has yet another rotor slapped on the end of that.

a 20b is a lot more expensive as you have one more rotor, so a proper engine management system is needed (such as a sport 2000), but once you got that, it will bolt right up to the tranny.

then there is the exhaust. some people keep it non turbo as they seem to make around 250 to 300 wheel hp in non turbo trim, and in turbo trim? 500 to 1500 wheel hp.