Wow , as I said this is my first time to use Elixir strings . Since it's been so long since I played and bought strings and I couldn't find any Guild strings, I just didn't know exactly what to buy .
When your guitar was made Guild was actually having D'Addario make their strings for 'em, at least the PB Lights, as D'Addario had introduced the formula in '74 and Guild was one of if not
the first to actually make guitars with 'em as standard equipment.
Sometime around the move to Corona, Fender dropped D'A and used a Mexican maker they owned (Squier, IIRC) and those strings weren't quite as good.
On close of Tacoma they got out of the string business altogether for a couple of years before getting back together with D'Addario in New Hartford.
On close of New Hartford they got out of the string business again, (why they're gonna be hard to find) and I'm not sure what Cordoba's installing on new guitars.
When your guitar was built, the set would have been the Guild version of D'A's EJ-16,
uncoated PB light .012-.053, with a quirk: Guild's version, known as "L-350" used an .025 G whereas EJ-16's use an .024.
When they got back together with D'A in New Hartford, they started using D'A's "EXP" series
coated PB's, and actually went to
mediums on dreads and jumbos, but that was following a lot of spec changes to things like bracing (went to red spruce, actually carried over from Tacoma designs) and top radius.
It's possible your bridge lift was aggravated by using mediums on a guitar designed for lights as Neal said.
I've been using D'A's EJ-16's ever since I put my last set of L-350's into "reserve", and buy an extra .025 single which D'A still offers to replicate the original Guild gauge selection, and my dreads' necks still have spot-on alignment with the bridge and no bridge lift.
Bridge lift is also partly a result of the way Westerly built 'em: they lacquered the top before installing the bridge and left a bare spot to glue the bridge on afterward, but that spot was a little smaller than the actual bridge outline, so there was always a little edge of finish underneath and surrounding the bridge.
Because the hide glue bond to the bridge is stronger than the finish bond to the top, over time excess stress on the bridge can cause the glue to pull the finish up and create that gap at the back of the bridge.
I actually have that problem on my F65ce, curiously, on a guitar designed for
extra lights .010-.047.