UPDATE:
I got the XR-7s wired up. I had to get new pickup rings, since they had flat, slightly undersized rings on the Burstbuckers. The bit that the double adjustment screws goes into had been removed, so I was able to use regular humbucker tapered rings. Not quite as big as the original Guild rings, but they do the job.
i went with a series/parallel/coil cut on the bridge pickup. It had more of a difference between the sounds than with the neck pup. One odd thing, when they were all wired up (according to the Dimarzio wire codes) I was getting an out of phase effect with the pickup selector in the middle. I double checked my wiring, and I did have it correct according to the spec. I reversed the neck pup's wiring, and it was back to full strength. Somehow they were reverse wound with each other.
Weird.