Getting the carb mixture and such "right" is one thing that your existing dwell/tach is designed for. For the driving items, it might be best to just use the speedometer for those notations, AFTER figuring the mph/1000rpm in each gear.
As a better tuning aid, there are some cell phone aps for download (usually low cost) that will serve as a chassis dyno of sorts. Have to have one of the "phablets" that have accelerometers in them, I suspect (which usually takes "flip phones" out of the mix). Probably would need a firm phone mount for this to work best?
What I got in the early '70s was a Radio Shack Micronta (brand) dwell/tach unit. Sits on the fender. 0-6000rpm range, with a 0-2000 range, distributor dwell, point resistance, voltage, with a swith for 4-6-8cyl. Not something to use "mobile", though. Not an accurate dwell readin gon electronic ignitions, though, or rpm, but can still be used in those areas. One thing I like about it is the cleanness and detail of the scales and needle.
Sunn used to have some really neat "roll-around" meters for basic tune-up stuff and also an air/fuel meter
Already have a "dial-back" timing light?
Once you figure out the mph/1000 in each gear, no real need to add an "inside" tach that's not already there.
ONE thing to remember is "mechanical error". The good accessory tachs of the '60s-'70s were 2% of FULL SCALE. So 2% of 6000 is less variation than 2% of 8000. So, if you are going to be a stickler for accuracy, the lower rpm scales are best. But for a general reference situation, rather than "exact", anything will do.
Just some thoughts,
CBODY67
