fuel injection pump mounting diameter?

[neimis]

I have a '92 Passat TD with the "eco" AAZ.

Giles is building me a new performance pump, but needs to know the "mounting diameter"of my old pump, which is, apparently either 50 mm. or 68 mm.

The catch is that I want to swap in the new one when the old one is removed, so it's a bit difficult to look at it. The other catch is that I don't know exactly what I'm supposed to be measuring :oops:

My pump # is 0 460 494 323

Does anyone know what pump diameter would be on my car? Any help appreciated, Thanks!