All the Guilds I know of from this time period came with plastic nuts and saddles. (Maybe Custom Shop Guilds were outfitted with bone?)
FWIW I've replaced all my plastic saddles with bone. I used to replace the nuts with bone as well, but I coudn't discern much change in sound, whereas bone saddles make a difference I can hear.
Yea, I’d go with bone as well, after all I am called boneman lmao , No but I just bought several blanks to carve my own custom ones. So far I got some practice on cheapy acoustics, and turns out it’s not so hard at all, so now I plan to carve new ones for each guitar as they need em. Should you take it to someone, any material to get the job done of course, but bone looks cool too.