My recollection about the classics is that these were ordered by Jay Wolfe and had Gibson-like bridges and tailpieces. I also think they had SD pickups. The maple neck was common back then but inconsistently done. I've had a one piece, two piece, and three piece on H-555s made in that era.
Custom select could mean anything, but the select probably refers to the woods. They probably charged extra money for each of those two words. Currently those words are custom core.