I just bought a tach for my non-rallye cluster. It looks like it will pop right in the smaller far right opening where the clock would normally be. I've only seen a picture, it really looks factory, but is described as new. Could you get a tach in a non-rallye dash back in the day or is this some aftermarket piece? I'm thinking it's aftermarket. Has anyone used one of these and if so, is it accurate?