Parts Store Inexperience

Went into the parts store one day. Asked for plugs for a 1970 Dodge Dart with a 340. He looks in his computer and then informs me a 70 Dart never came with a 340. I say yes it did. He tells me no if it did it would be in the computer. So after a few minutes of this I tell him look up a 70 Challinger 340That worked.