The listing is correct. I checked a signal mount on one of my '75 GL1000 parts bikes on Sunday, before referring you to the above listing. The threaded hole in the '75 headlight stay is LARGER than 12mm, (which would be 14mm) & I even took a 12mm bolt with me to confirm this. Furthermore, the 12mm signal stud is too long for the shallow hole in the GL1000 signal mount, and there is no room for the extra length and a nut; it will bottom out against the triple tree clamp. This signal post is the same on all GL1000 models from 1975 to 1978. If you have a 14mm thread on your headlight stay, the signal studs from '75-up will work.I believe that listing is incorrect. Those stays should fit 75 - 77 model year, but not 78. I do not have another to GL1000 to compare to, but believe 75 - 77's have M12 x 1.5 threads, where as a 78 has M14 x 1.5 threads. Partzilla shows a part # of 90129-431-670, only used on 78's.
I found a M14 x 1.5 oil drain plug fits fine. I'm searching now for a insert to to reduce the hole to M12 x 1.5 so I can use the more avalible stays.
Basically it will have the same appearance as the CB550 or CB750 that uses those signals. Most people won't even notice, after all, you would still be installing factory Honda signals. A vintage Goldwing guy will notice, but to anyone else it will look just as factory as the low-mounted ones. The CB400F 75-77 did the same thing, mounting the front signals halfway down the fork tubes. But the 350F had the older spherical signals on the sides of the headlight, & most people don't even notice the difference, lol! The 400F also used the big flat signals like the CB550 & CB750, and again, most people didn't eve notice!Thanks for checking that on your bike. It gives me more search options knowing 75 -78 will work. Your right I am trying to fix up this bike on the cheap. I don't want to get into a situation where I have way more money into the bike than what its worth. Always going oem can get you there quickly.
I like your idea of moving the turn singals up to the headlight. I'll see how that works.