Originally Posted by
PLR
I agree with DoubleChevrons reply .
You seem to have the information but have trouble putting it together .
The figs you give for the pump gears tell there is a variation of over 4mm .
The bottom plates are flat the extra distance is inside the pump cavity , if you fit later taller pump gears to an early timing cover the gears can`t rotate .
There are 2 gears one idles on a post the other is at the end of the distributor drive .
Changing the drive from one type to the other requires not only the changing of the drive type but also the pump gear or pair of gears .
Nunawading ignitions , i think it is , can change the diaphragm in your vacuum advance , they will return post it . Don`t remember the cost .