How big is this bus? I wouldn't put anything bigger than a 202-210duration@.050 to keep your off idle torque. Your lift at the valve on the stock cam is .397 if it has a 1.7 rocker which it most likely does. I would probably go with a cam around 208@.050 and as close to .500 lift as possible. Probably won't find one with much more than .480 lift from a cam grinder with that duration. Try to find one with an LSA of about 110 or 112.