Has nothing to do with being a racer. Some of the thick headed people on here have no clue how far under headed these 4 inch stroke engines are.
The architecture of these heads was laid out in in what??? 1962?? For a planned displacement of what? 340 inches? Maybe. 360 at the most.
And at what RPM? There were PASSENGER CARS. Cruise RPM was 2500-3200 depending on tire diameter and gear ratio.
And that’s with a rod to stroke ratio of 1.85.
Now add 68 inches and drop the R/S ratio down to 1.53.
You can go round and round with these guys and they’ll never get it. These heads are way undersized for the displacement.