Pollution one has a threaded boss on the driver's side for the thermal switch. The thermal switch is in series with the switch on the 3 or 4 speed top gear selector or on the back of a trimatic. When the vehicle is in top gear and warmed up these two switches connect the vacuum solenoid up on the motor to the 0V terminal of the battery (via the body), so the solenoid operates and allows full vacuum to the distributor. I think this is the only difference. When I put a Yella Terra 186 head on the 202 in my WB tonner, I put a little angled metal bracket hanging off one of the rocker cover bolts that held the switch in roughly the right place, and soldered a little bridge across the terminals under the switch. In my case the Trimatic in it was an early one so I just put the wire at that end into a ring lug and under a gearbox pan bolt. That way the solenoid was always on, and the dizzy got vacuum advance all the time.

Thanks for the information fellas.