You‘ll still be dealing with windage loss with any B or RB deal. Easily a 50 HP killer right there. And there is very little you can do about that. Not even a dry sump will fix that.
Do you remember PS Truck? I do. 358 inches in IIRC a 2800 pound truck. With truck aerodynamics.
And yet, if you analyze the numbers you’d find that the PST, if it was given a 2500 pound chassis and another 50 inches would be right there with PS car.
Everyone knew it. The trucks were far more popular than the cars were.
And the PS engines use maybe, MAYBE a 3.700 stoke. Most times it’s under 3.700 depending on bore.
EDIT: I forgot to mention at least 2 inch longer pushrods on the B engine. That’s an RPM killer right there. I can tell by the way you talk you’ve never had an engine at 8000 rpm with a reliable tach. You’d know how much the little **** adds up. And it adds up. Quick.