Welcome to the site, Greg!
My first advice...?
Hit your local junkyard. 73-88 Chevy trucks use the most plain Jane glass gaskets that you could imagine. Just stroll the the yard until you see something that you think would work.
My 1983 AMC Eagle wagon is sporting the parts of a '92 Eagle Talon (hatch seal), a '95 Dakota pickup (rear junction block for rear brakes), '86 Ranger clutch master cylinder reservoir, '92 Jeep Cherokee rear leaf springs, '75 Jeep CJ-5 transmission mount, and '97 Olds 88 E-Brake cables.
Stalk the boneyard!
