The '71-'72 engine paint was unique to those two model years. Most of the repro cans you will find have a little too much powder blue and not enough teal in them. The only spray can available that was correct that I've seen is the OEM brand that priced itself out of the catalogs of pretty much every Pontiac parts company around. It was running about $60 a can up until around 2008 in most catalogs. Since then the only way to get it is direct from OEM in 3 can minimum runs for about $210 total with shipping.
The other way is to have it mixed with the formula that is posted on the link below which will give you the correct color or as close as I've seen similar to the OEM brand.
http://forums.maxperformanceinc.com/...=719594&page=2
You can also order it in pints from Scott Tiemann at Supercar Specialties at 517-647-2433