OPINION ON DISTRIBUTOR

That is so odd that the MSD instructions lay out advance numbers in crank degrees for everything except the vacuum advance. DOH!

There is probably a way to limit the vacuum advance via a hillbilly engineering method. It won't, or shouldn't activate in any condition except constant throttle position cruising. I think it said 15 pounds of vacuum, should be 15 inches, to activate the vacuum can. Since you are barely over the threshold, it shouldn't be much of an issue. Any roll into the throttle should dump vacuum below 15" in most cases.