Re: 540P (Skolnick) /P2 question
While I would say they switched to the neck with a block inlay for model year 1990, I don't think it was an exact science back then. If during the 1990 model run there were still some leftover necks lying around from the previous year I would think they would have used them....especially an early built '90 model built in '89. Or it could simply be that they used a picture of an old guitar in the catalog.
I think seeing a non-block inlay neck on a '90 is probably more likely than the other way around.