Vacuum Pump Drive Gear Sizes

[Piper106]

Went to replace the diaphragm vacuum pump on my 1981 1.6 NA with a vane style pump.  Trouble.  The vane pump I have has a lot bigger drive gear on the end of the pump shaft, the gear is too big to go through the hole in the block down to the gear on the intermediate shaft.  

My question is what year did VW change the size of the hole in the block casting and the vacuum pump / intermediate shaft drive gears?  Are there any vane pumps with the small drive gear that would fit my block?

Piper106

[hillfolk'r]

a1 and a2s had same gear,,and a2 has vane pump,,you have a later pump,,like from a 1.9 or something,,my 91 has a 1.9 that my dad put in and it has a larger gear,get an a2 pump,,pretty common,,,heh i cut one upfor a prelube tool,,