One of the sportsman experts would need to leap in here, but, IIRC, the F- and X-Body subframe used similar parts to the A-, but the geometry was substantially better.

There was also an ad in SCR for a kit that used the front subframe, but added the rest of the structure to the rear taking advantage of the improved handling.

Bucks up guys had the Howe chassis starting about this time of the pic (note sponsor on door) which knocked out a lot of the home-brew production chassis after a year or two.

That said, there may still have been promoters keeping production chassis classes alive so the fields (and grandstands) were full on Saturdays.