May I suggest you trace the wires connected to the speedo out and find out where they go.
the Electronic VDO guage does not care where you get pickup, hence you may find that it was to be going to the diff. and got pulled away.
Depending on the trans, you can connect it there or anywhere a steady proportional signal is provided. The TKO600 two prong connector for speed is completely compatible and a connctor can be purchased from JimiG.
Hope this helps.
