Measure the runner length. The Single plains are pretty good for what they are. While not updated in decades, they really don’t need to be. The draw back is the runners are curved due to one carb inlet. It is what it is. I had Charlie Servidio test the W2 Holley Street Dominator, MP - M1 and the MP TR (pictured earlier) to see how the did. The problem we faced with the tunnel ram was a really bad port mismatch at the floor.
Of the single plains, the Street Dominator flow 280+, the MP street intake went to 300 IIRC, on both intakes.
The tunnel ram was better of course and should show that approx gain as said above pretty easily I think since the runners are straight and allows a really good straight shot to the port.
In the future after the heads are ported, Charlie agreed we should re flow the intakes. The Holley has been sold, so it’ll just be the M1 single and the TR.
You’ll have to check Charlie’s video to see the tests and results.