If you want to look period correct, Sun makes s repro of their vintage tach-looks cool and works well strapped to the column with a hose clamp! Patrick
Since this is posted in the street/strip section I will assume you would like a good tach for racing as well as street, so as has already been suggested, Autometer all the way. Mine is a 5" memory, which is nice to have. A playback, although a little more pricey, would be even better. Also worth mentioning, Autometer is an excellent company with superb customer service. It you ever have a problem with any of their products they are quick to remedy it.
VDO had one with a chrome housing that had the splined/grooved outside that was a nice match for a 66-67 dash. I don't think they make it anymore tho. For a factory look, a repo Chevelle tach fits the bill. It's made for under dash mounting. Avail on eBay: https://www.ebay.com/itm/1966-66-CH...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
