The manifold choke at the outlet, that is tough.
I don't think 325 or so is hard with manifolds.
I built a 69 340 .040 very mildly ported x heads 245/
[email protected] , stock iron 4 brl and exh manifolds and it did well with an isky .485
[email protected] 108 in 4*adv iirr.. or some ****. 'He wanted to stay with his old cam' but it still went into mid 6500 rpm horse powered well for manifolds.