No one can duplicate the paint process employed on 1st Gen Camaros. Even if you could, you would not be happy with the results. I have seen plenty of original paint 1st gens in my 49 years of the hobby. The process was designed for speed, not a show car finish.
It is not a factor in Legends Judging: "Paint is judged as condition only; and color must match the trim tag. Both show quality paint and paint replicating the original lacquer finish are accepted."
IMHO, the main problem is the clear coat that has to be used on metallic colors. Limit the amount of material on the car. The painter that did our cars would mix base with clear for the top coat, looks far more original. Leave some light orange peel, never clear over the stripes.
Prime System: In the first prime booth, the entire body, inside and out, was manually sprayed with [gray] primer, and confined areas subject to corrosion were given a second coat of heavier primer material; this prime coat was then baked at 390F for 30 minutes.
The second heavier coat was red and limited to the area around and under the rear window.
The interior color areas were masked, and the entire outer body was sprayed with gray primer-surfacer and the body was baked again at 285F for 45 minutes.
The vertical surface of the firewall appears to have little to no primer.
Undercarriage finish is a separate topic.