I wire a lot of hot rods from scratch, and I always put the disconnect on the negative side. That way, when it's swithed off, the body & chassis is no longer grounded, making it impossible to ground out to the body or chassis. It really doesn't matter though, as long as there is a break in the circuit. Put it wherever is easiest.
(Message edited by humboldtboarder on March 25, 2007)