1971 340 paint ?
Are you asking about the engine color?
If so then it is the Turquoise color. You can get the Mopar paint from the dealer mancini and other places.
If you prep the engine right clean it real good the spray can stuff will come out just fine. It is think so be sure to not spray too much and cause runs in the paint.
I even saw once on tv a guy wire wheeled the block so all the extra bumps and stuff came out smooth. It looked nice but seemed like a lot of work