to all concerned... oval port heads are only good for low HP application, on 454 ci and smaller, if you want to make power rect port is required... we are running in the water under load with throttles open and thats why a rect port head is required...

heads
 

i have one set gm rion .20 minutes run time on virgin casting. stock valves and springs for flat tappet cam. 500.00 plus ship

marine high perf engines run under constant load and with throttle open, a large displacement engine in this application requires hi flow, it is true that in certain applications an oval port will make better low end torque, but doesn't provide enough flow for the demands of a big engine running hi RPM
(5000++)
just my 30 years of building engines talkin, no malace intended

On 454 the oval ports will probably make more horsepower across the board.
Generally speaking, 540 and larger the rectangular ports have the edge.
Procharged? I think rect would be the ticket, but not much experience.