Hi Will, welcome aboard!
Be aware Guild themselves offered the same case(s) for both flatback and archback guitars, there was no special "deep" case to accommodate the arched back.
That being said, I suspect the cases and padding themselves were deep enough and had thick enough padding to handle either type snugly. My D25's OHSC is the "standard" (flat topped) type case and it
was pretty snug until the padding started to conform to the shape, but there's a clear imprint of the bridge, strings, and fretboard in the top padding now.
TKL was their primary case supplier during '90's, they may have something to offer I think Guild's case p/n's incorporated TKL's model numbers, but not sure.
This price list shows the Guild cases offered in '96, and note there's aso no special case for dreadnought 12's, so headstock clearance was also "built-in":
The "standard" (4500) cases were flat-topped and din't have quite as plush a lining as the "deluxe", more important, the "deluxe" (4520) cases had arched tops, primarily for strength, but maybe offering that extra bit of clearance you'd like for the bridge/pins.
Used cases do pop up on the usual sites.