What is the best way to put a shaft drive motocycle engine in a chain drive 4 wheeler?

Hey I am currently putting a chain drive motor on my shaft driven four wheeler and I am going to use a 90 degree gear box which used to be a steering box from an old dump truck I got. That gear box would probably work for you as well if you put a sprocket on the output side and hook the input shaft to your motor with a u-joint. Hope that helps