Correct. Not sensible at all. Except so much more sensible than retro-petroleum stuff.
Watching my brother-in-law buy a 1971 Chevelle for his 16-year old daughter because she thought it looked cool only to have him sell it at a fat loss 3 months later because she couldn't choke down the gasoline fumes driving out of the school parking lot every day was instructive.
Sounds like the dude needs to learn how to fix exhaust leaks.
Or tune the engine correctly. Probably has an off-the-shelf "performance" carb that's set much richer than it should and a "full race" cam that only makes sense for a track car, giving horrible fuel economy and actually less low-end power.
My daily driver is roughly as old, has a 400 V8 with a 4-barrel, idles so quietly I've had passengers surprised that the engine was running, and gets around 20-25mpg if I resist the urge to open it up all the way.