For the vacuum its basically around stock engine vacuum. I’ve pretty much picked the cam a while ago. Its from the company who makes performance cams that produce good vacuum. Lift is .515/.530 and its for 1000-5500 rpm. That 60’s high rise intake and some good oval ports should really wake up that old motorhome engine. You can still see the crosshatch pattern in the cylinders. New oil pump, bearings and piston rings would be a good investement. Gotta switch out the oil pan too, I dropped it in a car and the pan didnt clear the frame. Are exhaust manifolds worth changing or it wont make much difference?