Duncan started offering short leg baseplates for standard humbuckers in the early '90s.
You're less likely to find a paper-labeled JBJ/JBL with short legs, but they do exist as there is some overlap in that time period.
You're far more likely to find a printed label JBJ/JBL with the short legs.
Of course, you could also get a "Trembucker" (TB4J/TB4L) as those have had short legs from the beginning. The Trembucker spacing is also likely to be better suited to your Charvel.