[Cobra 29]

I use a vac adv module and connect it to manifold vaccum for better idle mixture burn (my wife complains less about the gas smell), trouttle response and better mileage. I using an MSD 8478 distributor that came with a vac adv module but you cannot limit the amount of vac advance. The Crane vac adv unit is also completely adjustable. It uses a small stepping plate designed to mount within a GM distributor to physical stop the advance. This did not fit the MSD easy. The Accel vac adv is adjustable is the amount of degrees of advance and at what vaccum the advance starts.