Re: long pickup pole pieces
I just pulled out a DD and gave it a look. The screws protruding from the bottom of the pickup were no longer than the baseplate feet. I have run into mounting depth issues before but they are normally related to the vintage style long leg baseplates. If you are having problems with mounting a 59 or another SD pickup with the long legs I'd suggest getting a pickup with the short legs. Short leg baseplates are available on almost all SD humbuckers.
If you already have the short leg baseplate and still need more clearance you can cut back the post screw ends that exit the bottom of the pickup. There is a rumor around that some players (one or two that I know of) like the tone of HB pickups better with the screws cut back. At any rate it shouldn't have a big impact on tone.
The thing is, you are still stuck with the mounting feet length and there is no easy way to cure that short of cutting the guitar. The cleanest way to do that is with a router and a HB template but you can do it freehand with a drill if you work SLOWLY and apply a little patients. Basswood is pretty soft and too much muscle will get you a hole in the back of the guitar which is not a good look.
Another often overlooked option with guitars that have special needs pickups is to send the stock pickups to SD and have them rewound to whatever spec you like. It's fairly easy to have a stock pickup re-wound and re-mangetted and just like magic your stock pickup is now a JB, DD or whatever it is you want.
I'm fairly certain that a rewind is comparable to the price of a new SD pickup but you'd have to call to SD to make sure and to get a RA number.