noob needs help with mileage - only 10 MPG!

To clarify: Linkage hookup is by year and application, not by carb manufacturer. There were both Carter BBS and Holley 1920 carbs for the rotating-rod type throttle linkage used on '60-'66 A-bodies with slant-6 engine (except '65-'66 with factory A/C, which used cable).

As has been pointed out, the 1980 engine will have solid lifters that require periodic adjustment. 1981 was the first year for hydraulic lifters (except for a small production test run of hydro-lifter engines in 1978).

I don't agree that the present mileage is reasonable. It doesn't look as if the vehicle owner has availed himself of the advice that's been offered in this thread. And I disagree with what the mechanic (is reported to have) said in response to the vehicle owner's inquiries; I question the mechanic's knowledge and competence.