I am not an expert, my I will try to help:
Most Fender Jazz bass pick-ups are two different sizes, but...
At least some of the Fender Squires (like the one I had) both pick-ups are the same size, which throws a monkey wrench in replacing them. that was the main reason I sold the Squire I bought in less than a week. I think EMG makes a direct replacement set, and somebody else does (don't remember) - but most companies do not. Bummer I know - that's why I ditched my Squire.
Also. FYI, my tech, (who is pretty sharp) wasn't even aware that Jazz basses hod two different sized pick-ups, to the point that I don't think he ever believed me.
The worst part is that the original pickups in the Squire 5 custom I had were crap.
Mark