I had one back in the 70s. Had the Road Wheels with 4 clip rings, a 69 type fold down ash tray, and automatic trans with the neutral start switch on the trans like a 69. Could a mid summer 68 have a few 69 features? I realize the wheels could have been a dealer swap if a customer had a preference

Tilting ashtray replaced the slider on the later '68s, I've had both - I don't recall all their SPDs, but I'd guess mid-model year.
Wheels could have been Ford Magnums or a swap; most of us modified our cars back then, or the originals were stolen, or were steelies...
Not sure what you mean on the NSS, all of mine have been on the trans - do you mean 2 vs 3 pole switch ?

I've seen a few 68s with a trans switch with just 1 wire, and another switch on the lower steering column. I figured they must have simplified it sometime during the 68 year model. I've learned there's nothing carved in stone about the way these cars left the plant.

According to the factory parts catalog, that change took place on May 15, 1968. The parts catalog is a good source for when and if changes took place during a given model year, it will list the old and new P/N and, usually, the date the change took place.

My 68 RR is also a later build - SPD is May 4 (Lynch Road). It has the tilt down ash tray along with the single wire NSS and the reverse light switch at the bottom of the steering column. It is a post car without the decor package. It also has the shoulder belts which were mandatory after 1 Jan 68.

if i'm not mistaken, the early build cars with the console shifter had the reverse light switch on the shifter when they had the single wire NSS.
then the 69's and the very late 68 build cars with the 3 wire NSS used the same shifter, but with a different console top and shifter knob, and the shifter still retained the threaded area where the early reverse light switch bolted up.
at least that is how the shifter is in my 69 charger, and it's the original shifter.
i have owned the car since 1970.