The wheel sizes are the same until the 1982 models. I'm not sure if the speedo drive will fit both, but I got this piece about what parts are swappable between the 1000 & 1100 from the FAQ page;
[align=left]Q. I've been told that some GL1100 parts are the same as those fitted to the GL1000. Is this true and if so how many parts are like this please?[/align]
[align=left]A. Yes, quite a few parts are interchangeable between the GL1100 & GL1000. The GL1200 in comparison uses very few bits from the parts bin. Some of the parts shared between the GL1000 & GL1100 are; Front & rear engine cover gaskets, valves & valve springs (up to 1981), valve seals, rocker cover gaskets & sealing washers, timing belts, timing belt cover gaskets, oil filter & drain plug, clutch springs, exhaust gaskets, ignition switch assembly (1978, serial no. 4104123 & up), starter motor brushes, starter clutch rollers, front & rear wheel bearings, front brake master cylinder & reservoir repair kits (up to 1981), front brake pads (78-81) front brake pads on the 75-77 GL1000 are the same as rear pads on 80-81 GL1100, brake lever 79-81, clutch lever 78-81, rear lamp unit lens 79-83. Heavy duty aftermarket replacement stators will fit either model as well. I've probably omitted plenty of other items, but you get the general idea.[/align]
I really don't know what year gauges I bought as I got them from an internet sale..delivered from FL. The speedo is off though. When I bought it the fellow said it was a 79--OR?? GL. .however he owns a salvage yard..and not a GL enthusiast..just a parts seller. He was the guy that told me the gear in the two bikes for the spedo were different.
The temp gaugeis NOT in the tach like my '76 stock gauge..and it is black faced if that will identify it.
I order to check it..they had one of those radar speed checks in a construction zone. I noticed it while on my 1800C VTX. I ran through it twice..the speedo was very accurate. 45..and 55 MPH read very close.
I went home, got the GL, as I've always knew their was a error. I went through four times. Each passs yeilded a error of approx 20% low.
The seller had offered to sell me the correct gear for the speedo..but I never got back in touch with him.
Thanks..I'll check some more..
I lie the black gauges..and have run without a temp gauge for 5 years now..IN ARIZONA..but the bike is a cafe and dosen't see very long distance..100 miles is a good ride for it..
I've had this bike since new..and it ain't going away ever...