In my Ghia I'm using a full line of Autometer guages. I tried to figure out a vw sending unit, but I ended up going with Autometer's guage for their sending unit, it's the same bolt pattern, you'll just have to make it fit your tank. Since it's universal. Personally, I'd rather go with a guage and sender that I know for sure work, then try to take a guess.
I'm also using an electric speedo, but I got my sender from speed"o"meter service co. in Milwaukee, WI
www.speedometersolutions.com They were good to me, but I've only bought 1 sender from them.