soo...there is a little plastic piece that goes on the limiter pin for the centrifugal advance similar to the chevy hei, if initial timing is 5 it stops it at about 28 ish, every distributor i have been in it had already broken and so i never noticed it, if you don't have it it allowes the advance to go around 5 degrees to far, if you still have the second spring that i removed from mine it's no big deal because it advances slowly enough to not do damage, but without the spring it causes issues.
i found in the bottom of the dizzy the remains of the bushing and made a new one, then i re timed it and we shall see how it turns out but without the bushing it was causing a slight detonation, i was doing the normal 12500 mile maintenance and pulled the plugs and peaked in the cylinders and it had caused what looked like silver specs on the pistons which is the sign of slight detonation.
so if you do this mod make sure you have the bushing and i recommend only 5 degrees of initial timing (if you don't do it then your engine might like as much as 10 of initial).