Questions Regarding 383 Barracuda Engine Compartment

I was there in 1968 and ordered my car personally as I worked at the dealership. P/S was not on the order list nor was A/C if you got the 383. This car arrived at the dealership April/May. It was manual steering. You would think that was a "late" 1968. I have since acquired another similar car WITH factory P/S. This has an even later production, closer to the end of production. How did they do it? The exhaust manifold on the left side is different making P/S available. So for 1968 there are two different left side exhaust manifolds, which is why when ordering new exhaust pipes you will be asked for the casting number on the manifold. So for '67-'69 cuds's (maybe Darts too?) all manual steering cars used the early style manifold, whereas late '68- '69 cars with P/S use the later manifold.