the GMC has a "Y" shaped intake port runner over the Stovebolt's "T" shaped port is a huge flow improvement
I agree - that's a big step.
Another mod that's easy to do, and nice to have: increase the ID of the pushrod clearance holes so that 3/8" OD clears.
If the head thickness (top to bottom) should resemble the 235, you have about 1" of extra valve stem height that allows you to raise the entire port wall and make the ports downdraft.
