ya don't normally mod stingrays or anything musicman related.
why? because they already do the musicman tone better than any other bass in the world. it seems obvious, but when you look at jazz and precision basses you can see how one might assume upgrades will help them - fender basses are wildly inconsistent in tone from line to line, year to year, version to version of the same "type" of bass (precision, for example). hence lakland and 50 or so other company's primary product lines being improved versions of fender bass designs.
musicman basses are already as improved as they can be.
you can mod them so they are no longer purist musicmans, but changing the pickup will either result in very little or no change (if you get a great after market pickup... it'll be as good as the original with possibly slightly different voicing). or you can get something that sounds unauthentic and use that instead (like a bartolini pickup in your stingray).
stingray classics are kind of the elite vintage musicman bass. they're made in usa by people who care, use top tier parts, the sought after 2 band preamp and basically ideal parts in all ways other than arguably the fact that they choose to be REALLY authentic and not put in body contours, which irks some folks because it's not quite as comfy a bass on your body as many others are, even non-classic stingrays have body contours, but "classics" don't because they're a modern version of the classic vintage stingray.
Coupled with the fact that they are already very expensive basses for production models (classic fives are often around the $2000 and higher range in my local store), and they have excellent resale value in the used market, means modding one will cost a lot for likely little or no improvement and will actually devalue the bass.
EBMM has been very clever about their parts sales... they try to only sell to you if you can prove that you own a real EBMM bass and are searching for a replacement for a broken part. It's challenging, nearly impossible in fact, to buy aftermarket authentic EBMM stingray pickups and preamps.
Hence the aftermarket versions you can buy from other companies... which are typically compared against the originals in the classic stingray (or similar) to see how close the aftermarket versions get to being "authentic".
It's SO different from fender and other companies...