Iceburgh nailed it with the sender and part number. This is what you need. Then once wired together. There are a ton of websites out there for VDO that will tell you step by step on how to calibrate your speedo. I have VDO too... very simple to calibrate and very stable accurate reading.

When I got my car from the prior owner, they had ganged together 3 senders like the one Iceburgh showed. They couldn't get the last one to fit, so they put a 90 degree driver before mounting the last one. So much weight caused the tranny speedo drive case to warp and leak. I replaced the speedo drive case with a new one and removed everything except one sender.

Why three senders you ask? I have an LT1 engine and the computer needs to know the speed. They also had a separate sendor for the Speedo and one for the cruise control. I went to one and drove the speedo and cruise off of the one coming out of the computer.