Steve R, I have no idea why they did it as they did, it must have looked good on paper. I believe the new BBs have equal-length, non siamesed intake ports. I know the Pro Stockers do, and have had for several years. Warren Johnson had a piece of sheetmetal made to cover his intake when he got his first set of non-siamesed heads. The sheetmetal cover was to hide the intake port difference from the competition.
Also, someone mentioned in an earlier post that BB Chevies have 5 bolts around each cylinder; they do, except for one cylinder on each bank, which would have to go through an intake runner in the head. They did on the all aluminum ZL-1, with a cap on top of the runner for access to the head bolt. Pro Stockers may have used the extra bolt also, I don't know. They'd get persnickety if you tried pulling one of their valve covers to check.
