Before I owned it, Craig Taylor (Taylor Race Engineering, where Scott used to be one of the magicians) converted my Tiga from Hillman Imp axles to VW by making spacer rings which fit between the upright and the VW bearings. Scott can make something similar or maybe figure out something better.
Fun fact, Craig told me years later that mine was the only car he had ever converted to VW axles. The next time they had a Tiga in the shop, someone noticed that Mazda axles looked tantalizingly close to the right size. They turned out to be a drop-in fit. Not sure which Mazda the axles were from, though.
Oh, and about using VW bits: I was using Type 3 rear hubs, but they were made in Brazil of some material that was only slightly harder than old cheese. After a few races, the hub would deform to the point where the axle nut was no longer tight. The first time I found this out, the splines were ready to fail. The next time, I caught it when the hub was visibly loose. From then on I checked that hub after every weekend. The only good thing was the hubs were cheap (a local VW specialty shop had overstocked on them in the 80s) and the CVs and boots were easy to find.
I ended up replacing the hubs with semi-custom aluminum hubs with hardened bearing surfaces from Larry Oliver, but the next step was going to be steel hubs from Taylor Race Engineering.