Can I get away with stock 318 exhaust manifolds on Magnum crate engine?

DYNO tests showed 11 hp difference between 340 manifolds and std perf manif's
you wont feel 11 hp in the seat of the pants meter

choose you manifold gaskets carefully the ports are different on la/magnum heads

i have seen la gaskets in this config that leaked

most of the good gasket manufacturers make a gasket that will work for both manifolds