Can anyone verify the proper timing spec for a 1966 170-1BBL

[WH23G3G]

I've got this 65 Valiant 170-1bbl car running and idling pretty good. Driving around in my driveway which is a pretty decent size it does good. I put a reman Holley 1920 carb on it from United Carb Remanufacturing company. Put it on, a new fuel filter, plugs, wires, distributor, cap, rotor, and air filter. I didn't adjust anything on the carb except the curb idle, which is what the tech at United said is all I should have to do. It's a 1966 170 motor mileage unknown, inside from what I've seen under the valve cover is clean. Possibly rebuilt before. It idles smooth once warmed up for a minute or two and it has good power, but if you stomp the gas to the floor it pops but get into it gradually and it has good power. Is this timing, carb issue, or valve deposits from sitting for years without running? I put the timing on 2.5 degrees BTC which is the spec for a 65, because that's the year of the car. However, I found a 66 170 timing spec to be 5/5 degrees ATC Cap. Don't know what it means. It says on the heading under the timing Ignition timing BTDC or Mark. Any help?

[Musicman]

You can not time an engine today using specs from the 60's, fuel is completely different now, with different characteristics and different burn rates.

[WH23G3G]

That's the only way I know to do timing. I don't know how to tune the timing by sound like some of the veteran mechanics. I've watched some older mechanics tune 60s or 70s car without any specs and have it running and idling as good as a new car. I know the fuel has changed so keeping that in mind should I advance the timing and by how much?