As mentioned above, check speedometer accuracy. I've check MPH via google maps, a free app on my cell phone, and one of the school zone radar signs. Am fast by 4mph at 40 mph - 10%. Have also driven a 1 hr loop (or so) in my other 2 vehicles and noted the millage. Repeated the loop resetting the trip meter on the A and noting the odometer reading, and was off the same amount - 10 %. The A was reading 10% high than actual
If your A is fast enough you could check your A on an Interstate using the mile markers, just do it when/where there is not a ton of traffic.
I've also drained my tank taking the gas line off, filled it a gallon at a time using a milk jug, and marked a stick at each gallon. The marks are not linear. Especially when the tank going from 1/8th tank to empty on the gauge.
With large bias ply 16s, I get about 15-16 mpg rural driving on my late 30 CCPU at 30 -45 mph, this is with the correction factor of 10% I have 3.54 rear end, running w18 plugs, 4000 miles on a fresh rebuild (standard head, compression at 65lbs.), rebuilt carb (Zenith and Marvel, both get about same MPG), no air filter, standard trans - no Mitchell or overdrive. At this point I believe the tires are causing the low MPG, am willing to live with it. But your 7 MPG seems low.
Once you are sure your Mph/odometer is correct, look at your plugs, checking them after running 30-40 mph for a good half hour, no low speed driving. Press in the clutch, turn off the ignition, coast into a parking lot or some where safe, pull the plugs and see what the center porcelain is like, should be a tan color. Running at idle /low speeds usually causes a slightly rich condition (especially at low idle of 375 - 550 rpm), and around town stop and go - the porcelain may blacken - this is normal.
If you get a ton of black powdery substance you may need to adjust your Gav, or may need to; clean or rebuild the carb, install Renners Corner Flow tested Jets, or may need to run hotter plugs. Most vendors and some carb re-builders do not use flow tested jets, which commonly causes carbs to run rich.
If you end up having the carb rebuilt, I recommend Jim Bullock Texas -
https://jmacarbs.com/