As for me, I made a strap to fit my dashpad, back in 1971. It hooks under the frontmost edge near the windshield, is form-fit to the pad, then the inboard end is bent down and around the padded edge. On it, I mounted a 3.75"/8000rpm tach with a 270 sweep . On the face, the tach has a shift lite and a dial-type rev limiter. They are not as accurate as the high-end systems but honestly, on the Street they don't need to be, cuz who ever looks at them anyway?.
This tack is wired and mine is set up so that I can slide the thing into view on race day, and the rest of the time it is parked more or less under the mirror. I use the rev-limiter as a poor-man's cruise control. I set to about a a mile or three over the speed limit and so, when the ignition cuts out, I know I gotta claw back some speed. The pointer is set to 5000, cuz who the heck can see it anyway when blasting thru traffic. and it prevents people from commenting on my 7200 shift rpm that they don't know about.
The Shift light?
Well, mine is set right on the power peak to alert me that sometime soon I'll need to shift, but relax, it just means soon. The tach is not my boss. I'll go to 7200 if I darn well feel like it. Besides, 65 mph, in First-over is only 6900 and change, lotsa time; the tires haven't even stopped spinning yet. Juswait. Second is gonna get me 86 and Second-over is 109. Third, if I needed it, would get me to 116
Fourth is not a gear I often use. and 4-od is for cruising. 65=2240.
But I digress, lol.
The tach is an old Autometer.
I like it up top, cuz I'm 71, and my eyes are just starting to get slow to focus/refocus. I wore eyeglasses from the age of 15 on. But around age 65, I realized that I could ask Jesus for stuff, and so, about 4/5 years ago, I asked for better vision, and received. An eye exam released me from the scourge of having to eyeglasses for driving any more. and of course I no longer wear then at all then. I threw them away.
but I digress again. sorry, lol.