For people trying to retrofit 3rd party pickups to your 80's Guilds with three screw adjustments, TV Jones has an adapter available:
tvjones.com
Spacing for the bass-side screws on the TV Jones adapter is 5/8" (0.625") according to their tech folks. That's slightly narrower than the 0.75" used for the mounting rings, but there might be enough slop in screw tolerances to make it a suitable fit.
Dual Screw Mount Adaptor
Attach a TV Jones pickup to your Gretsch with our Dual Screw Mount Adapter. Keep your rings and replace those Blacktop Filter'Trons with ease!
tvjones.com
Spacing for the bass-side screws on the TV Jones adapter is 5/8" (0.625") according to their tech folks. That's slightly narrower than the 0.75" used for the mounting rings, but there might be enough slop in screw tolerances to make it a suitable fit.