hello more of a lurker than a poster but i like this topic
If I'm correct converters came factory on cars in i believe 1976 +-
fuel injection came on cars full stream 1986+-
also i have heard of many people with older cars getting 20 plus mpg with 6cyl.
and Hot Rod mag. got a 67 Camaro they saved from the crusher in 1993 and got it to pass Cal. emmisions.
1967 Chevrolet Camaro Drag Car - Hot Rod Magazine