What happened to yours? I think the shaft is the same for all the vw 8V engines. someone might need to back me up on that though.
The shaft itself is the same for the early cars (1.6, 1.7), but the gear on the tip is different. On the gassers, the gear is reverse-rotation to run the distributor. Frankly, I'm not sure how it would affect the old Rabbit-style vacuum pumps, but it definitely would not work with the vane-style pumps. But, you'd have to reverse the gear on the vacuum pump to make it work as is.
For schnits and giggles, I compared the PNs on two shafts I had: one a 1.6 gasser, and one a 1.6 Diesel. The PN stamped on the shafts were exactly the same, but there was the difference in the distributor/'vacuum pump gear orientations. It looks like the gear is "press to fit", or heat-fit, like the gears on a flywheel. So, if you were in a pinch, and had an old gasser shaft laying around, you probably could heat the end gear till it fell off of both shafts, and then install the diesel gear on the gasser shaft.
Good luck either way. I'd sell you a shaft, but I'm already short 2 from doing the same job just this week.