I ran into some similar issues a few years back on a GMC 228 with a Rochester Model B (Note: this engine currently resides in Dellrose, TN). It turns out that I had several issues: heat riser valve stuck in the hot position, a vented gas cap that wasn't venting properly, and a fuel pump pressure of 9-10 psi. One by one I resolved those issues. The hardest one to find was the new 'vented' gas cap. I can assure you that cap is vented as I type this response! It seems to me that a fuel pump pressure of 4-6 psi is adequate. I bought a fuel pump from one of our preferred vendors and the problem was fixed. Anything over that could possibly be trouble for the needle and seat.
The ultimate solution was an engine transplant. Today, a 1955 235 with a Carter YF resides in the engine bay. I believe Jerry says it like this, "The ABC's of carburetion------Always Buy Carter!"
