[samwise68]

a 4 barrel intake, coupled with a better flowing exhaust, such as a split manifold or headers, will improve horsepower, yes.

These 6's had a hard time breathing, with a one barrel carb and a single 2 inch exhaust, let alone the port design.

as far as a carb, idealy a 390 Holley would work great on a 250, but a 500 cfm carb works well too, it all depends on tuning.

if you haven't, jump over to ww.inliners.org and see if you can find some more info. they're dedicated to 6's,a nd know there stuff.

just my take.

-Sam.