With all due respect to ALL the outstanding restoration enthusiasts on this web site, I would suggest that you join and read the ORIGINAL forum at
www.nastyz28.com. If you were to search that forum you would find almost everything you could possibly want to know about 70 Z-28 restoration.
That being said we first of all need to know if your 70 Camaro was built at Norwood, Ohio or Los Angeles,CA ?
Norwood Camaros were primed with "Red Oxide" while L.A. Camaros received a shade of "Black" primer.
I have never read or heard of the specific G.M. formula, name, or number of the original Norwood "Red Oxide" primer.
PPG DP74 is a good underfloor/interior color (for 70+ Norwood Camaros) and has been used by many. Keep in mind that PPG did not intend for DP to go unfinished, as it can be harmed by UV light. Now I understand that the bottom of any Camaro wont get see UV light, but Im just pointing it out. Might be a good idea to top coat the DP with a Flattened Clear????
I have read in a magazine article where DYNACORN(sp?) is priming there New 69 Camaro bodies with DuPont IMRON 62-711 Red Oxide Primer.......and it looks very much similar to "whatever" was used on Norwood 70's...........
From everything I've seen at major shows, the top restoration shops and owners have a tendency to over restore paint finishes and plating, as that's what the majority of people want to see.
I still can not quote what formulation and percentages are to be used, but recently I have been impressed with either the GLASURIT or PPG single stage black paint mixed in varied degrees of brightness to achieve the mixed shading that factory cars have.
If you are media blasting to bare metal and correctly treating, priming, coating the metal, POR 15 would be the wrong product for restoration.
Jerry McNeish's Camaro books are one source of "correct" finishes for misc components......
I myself followed old exacting instuctions from a 1990's MUSCLE CAR REVIEW Magazine article where PPG Delstar Black Acrylic Enamel was used. While it intially looks good and may be OK for a show only car, I will not used it again for durability reasons.
Joey Gray's 2nd Generation Camaros (336-764-8856) in Clemmons, NC does a great job on restoring 70 Z-28's.