I need a little enlightenment on this Holley carb

No, it wasn't. 1973 was the last model year for Holley 1920 in a car application. Everything in a car got a Holley 1945 from '74 on. Trucks and vans may have used a Holley 1920 a couple years longer in some applications but I doubt it.

The earliest versions of the 1920 with a bowl vent w/tube used a plastic version. The last year or two used a metal tube like my '73 had.