My early '70 3/4T with a 402 BBC and 400 THM has the vacuum valve in the snorkel, but no pipe or sheet metal around the DS exhaust manifold. It has an exhaust manifold with no AIR fitting attach points on the driver's side, and an exhaust manifold on the PS with plugged AIR fitting attach points. I met my wife in 1980, and the truck hasn't changed in that time, to my knowledge (except that my FiL got it painted and the shop didn't paint the part below the lower molding white like it was from the factory. I busted his chops over that, and he busted mine back.
Not my truck! I realize that mine is a '70, but I guess that the factories did different stuff at different times. FWIW, I worked on spacecraft for many years, and while they conformed to the electronic communications requirements, mechanically they could be quite different, within the design parameters. One spacecraft program I worked on was spin-stabilized, and every one of them got balance weights in different places.