I have a recent set of Big Block Chevy heads from MBE in the Charlotte / Mooresville area. Study up on them. These guys are some of the best in the High Performance head market.
Dart Iron Eagle castings, CNC ported (both ports and chambers). Intake valve size is 2.350" and exhaust diameter...
Another "For What It's Worth" . . . . . .
I have heard that the folks at Sunset Racecraft in Lubbock (top drag race and circle track builder in this part of the country) have some extensive data on the subject of horsepower loss with an aluminum block vs. cast iron block with the exact same...
I wish I had a nickel for every race engine "fresh off the dyno" that would not accelerate under load (off the corner or up through the gears) until we changed the tuneup, or fattened up the fuel or something.
Steady state dynos have their place and are the most widely used. But the inertia...
For what it's worth . . . . . . . . ,
Back in the late 70's and early 80's, I built engines and was crew for the premier Drag Boat Racer of that era, Eddie Hill.
We held all four drag boat association ET and MPH records at the same time, bests of 5.60's at 226 / 229 MPH. Exceptional win...