Tried to go to the dealer for parts

The guy at the counter says the computer will not let him look up anything before 1984!

Does this guy not know what he is doing or is this the norm?

Why I went there:
I was looking for a lower balljoint to spindle bolt (unique head/length not available at hardware store) I was able to look up a diplomat to find the bolt only to find out it was no longer available. Interesting to me was the bolt was used in the 50s on up to 1989.

It's not the guy at the counter's fault. 1989 was 25 years ago.

If you could find a part number for it, you might get lucky and be able to track one down through the parts network but realistically no dealer is going to stock something like that in 2014. It would be really surprising if you were able to find one. The truth is that no one in their right mind brings a car to a dealer that's been out of warranty for over 20 years so there's no sane reason for them to stock that item.

There used to be a list floating around of parts still available for our cars at the dealer but it's doubtful that bolt would come up.

Best bet is the junkyard, here, Ebay etc.