Onto the next issue with my car (a 1974 with an apparently fresh but unknown build 1.7L with dual weber 40 carbs).

It's doing a fun trick where, about 3 seconds after I shut it off, there's a huge bang (backfire I assume) like somebody firing off a rifle right behind my head. Seems to do it pretty consistently. Not sure the gas station attendant appreciated it!

Any thoughts? Note the carbs are still jetted for the 1.8L I had in there previously.

For shits and grins try letting it idle for 30 seconds or so before shutting it off to see if that helps. Not necessarily a fix but could help avoid it.

Many of us just wish for "midlife banging"

Here you go.