The front end is made up of 76 GL1000 parts. Just about everything up there is GL except for one of the steering bearings (upper or lower -I forgot, but I did have to use one of the original bearing to get the tree into the CB frame.) The fork brace is by Markland which is aftermarket for those early Goldwings. Bought mine on ebay.
For dual disc with spoke wheel conversion, the front end from 75-77 GL1000 will work. I couldn't find a complete front end, so I bought mine piece by piece -forks, triple tree, wheel, discs, calipers, fender, and all the necessary bolts. As a consequence to purchasing items piece by piece, I ended up with two extra sets of front rotors, and extra set of calipers, and a set of GL gauges. Then, I wanted to match the back wheel with the front wheel, so I bought a GL rear wheel, and relaced the rim to the CB hub.
Althought finding all this stuff was fun and fairly cheap (not much peeps bidding against you for old GL parts), it's probably easier and cheaper to just change the fork oil, get progressive springs, and a fork brace for the original CB front end.