The truck in question is an 89 V3500 w/ 454 TBI. Right now the truck has the factory manifolds with a custom 3" crossover pipe and 3" single exhaust. I've been contemplating upgrading to headers and dual 3" pipes. I'm in a non-smogged area so I'm not concerned with the usual emission laws. Other than having to install a bung somewhere in the system to accomodate the O2 sensor(which is a 3 wire heated unit), what other things do I have to consider before undertaking said upgrade?