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So I got this kz750 1976 I believe but I got no title and just wondering if anyone would know what frames would be compatible, it's a twin kz750. Any help would be appreciated, this is my first Kawasaki.

I am pretty sure the only compatible frames are going to be other 750 twins. Might be easier to just get a title for what you have. If you are in the U.S., it may be easy. In some states it is easy, in others not so much. If you live in a difficult state, getting a Vermont title first might be the ticket.
If you live outside the U.S., then I do not know. At any rate, it would pay to check with your local department to find out just what you need.

The best match would be the 76-79 750B models. For swapping the engine I'm pretty sure you can go with any KZ750-Twin frame, since the motor was pretty much unchanged thru the entire model run. The 83-84 750K models were belt drive & I have no idea if that would be an issue.