My 360 build.

I did a 13.30 car on a cheap 360, and true street car (3.23 gears). Cam was MP .455 lift/268/272 duration. Idled like a stock cam. 750 double pumper Holley a LD340 (RPM eddy would work as well). Heads were J heads.
It really don't take that much to go low 13's/high 12's with a 360 in a A-body.