You only test one port at a time and an old chevy V8 won't flow much at all per port... after all some of the older V8's only make about 25bhp per port/cylinder! Even the latest 4v/cyl supercharged LS engines only make just over 100bhp/litre at 6.2l (80bhp per cyl) which is within the flow rates of the smallest SF benches assuming they're charged at more than about 3-4psi. I came close to maxing out the SF flow bench I used to use at about 65bhp/port.
Also it depends what pressure drop you test at, industry standard is normally 10 inches H20, but the bigger tuners that can afford benches that take up a room (thinking specifically Cosworth here) have capability to flow 1000bhp at 28 inches and test entire intake systems.

