Got a stock driveline with 3.55 rear.
Late 235 with duals intake and exhaust.
No head work, no cam upgrade.

18-20 mpg freeway
14-16 mpg city (4000 ft altitude)

All depends on your tuning abilities and the right carburetors, with a good engine.

On the road every day...
1952 Truck - 235
1948 Coupe - 261