The escort I've nearly finished 'breaking' didn't come with a rev counter.

I'd really like one, and I'd feel a bit daft having just put together a sports car without one!

I presume you can't just stick any old thing in and wire it up (not that I know how to do that either..... ) However I may be well off the mark!

Can someone point me in the right direction?

yeah, either buy one or rummage through a scrappy (we used the mechanism from one on an Opel Manta...) and usually there are 3 connections- one to +12v ignition, one to earth and the other to the coil. Easy Peasy.