High Performance Mopar magazine did an article on this in their 65 Coronet 500 that they had a 383 magnum motor in. I think they had a stock intake and manifolds, then extrude honed them and got about 5HP. Then went to an Eldebrock and got huge gains. Something like high 13's with a stock magnum exhaust system (compared to mid-low 14's)

I'm sure the Dp4b and the Weiand 8008 are better choices and look stock. The 8008 has a stock coil location, where the DP4B is righ in front of the carb. Which is in the way for my stock 70 Holley.

Maybe a 72 T-quad would be a better improvement?