Headers VS Manifolds

Here is a link to a Mopar Muscle OEM manifold and headers comparison on a dyno using a mild 360. The more performance you build into the engine, the better headers will work.

http://www.moparmusclemagazine.com/...pp_0307_mopar_crate_engine_exhaust/index.html

But I may have some bad news.....Watch for other problems if you had to lower the trans mount location. If everything is tilted down at the rear mount, it will mess up your driveshaft/pinion angles and can cause header clearance issues with the chassis! Too bad you couldn't have found a 904 because I don't believe 727's were available in A-bodies back then, so the floor pan and frame wasn't designed to make them fit right.