what tank fits what frame?

I'm new. have an '81 GPz1100 that is really a working rolling chassis and engine, with no bodywork to speak of. So, I think I'm going to go "mild custom sport bike" ala Ducati Monster. So, my first puzzle is, what is the difference between the frames wrapped around the 2 valve engines? Specifically, what gas tanks will fit on my GPz frame? Will earlier or later years fit? Will a police model tank fit? Will a kz750 tank fit? Any and all info will be appreciated!
Thanks
Grandpa Bruce

Welcome Bruce! Not much will easily fit an early model GPz1100 frame other than an early model GPz tank. So, what you are probably going to have to use is a 1981/82 KZ1100B1/2 (GPz) fuel tank, a 1983 KZ1000J3 tank, or a 1982/4 KZ1000R tank (the differences are paint schemes). The 1982 KZ750R1 (GPz) tank is way too narrow. Depending on how creative you wish to be, most other tanks will have to be fabricated somewhat (both fore and aft) or are too narrow.

Mcdroid wrote...
"Depending on how creative you wish to be, most other tanks will have to be fabricated somewhat (both fore and aft) or are too narrow."
Fabrication doesn't scare me. It's that narrowness that can mess things up. So the question becomes, If I'm willing to fabricate mounting points, and I'm only concerned about the way a tank sits well over the frame, can I assume that most '78-'84 KZ1000/1100 frames have the same basic shape, and that therefore I can pick the tank that most tickles my fancy aesthetically?

Grandpa Bruce

Well, I don't know if it would be as easy as you might envision...and I don't want to encourage you as I really don't know the answer to your question. For example, the front tank mounts on a 1977 Z1000A1 frame are on the lower frame tubes above the engine (there is a single median upper tube). On the GPz's, the front tank mounts are on the bracing attached to the triple tree. An overriding concern should be tank length, the GPz's are about 25" long while the earlier model Z's (900 and 1000's) are about 23" long. An additional concern might be that the electronics on the GPz wants to see a tank with two openings on the bottom (one for the petcock and the other for the gas gauge apparatus).:blink: