VDO makes 2-1/16" tachometers in the Vision and Cockpit lines that should do the job. I believe they get a signal from the coil and have a 4/6/8 cylinder setting to provide the correct display.

You might be able to put the tach in place of the clock like in a 6.3. Forget an original 6.3 tach unless you have money to burn.

You could get a big glaring 5" tach with shift light like they have in Civics but you don't want my advice on where it should go

Sixto
... stay tuned