Want to put and aftermarket tach in a rallye dash

My 68 was born with a factory tach in that hole. I tookit out and put a Vacuum gauge in there; that tach was too small and too slow. I put a 4"/270sweep,Autometer-8K, topside on a floating bracket. Now I can see 7000 coming, right in my line of sight; no searching in the dark with ever increasing speed.
And when I'm cruising, I just float it off towards the passenger side.
Or maybe it was an AutoGauge, Can't recall. It came with a lil shift light and an adjustable rev-limiter, whoot! I set the rev-limiter to 2250 when I'm cruising 65mph. No speeding tickets for this cowboy.
It also came with a shift-needle that I set to 5400, just cuz.