The E-Class flat bottom circle boat I crewed on in 72-76 did 8,500 rpm with push rods, but it wasn't easy or any where near streetable. It was a 327 Chevy with a Weiand tunnel ram, dual 600 center-squirter Holleys, custom cast heads with BB valves, Sig roller cam with a ridiculous profile, a prototype BRC "Rev Kit" (helper springs under the intake to keep the push rods from floating) and a Vertex magneto. It dyno'd at about 800hp on 110 octane race gas. The boat owner had $26k in '76 dollars in that motor and we did win our class at the nationals that year. I think the grand prize was a couple cases of oil and plugs and a kiss from the race queen.