The bike you have is most likely a 1980 KZ 750 G-1. If it´s red and has sidecovers that say "LTD 750t". The LTD had solid wheels, stepped seat, and pullback handlebars. The ´76 - ´79 models were the KZ 750 B-1 thru B-4 (respectively). They had straight bars, no stepped seat, spoke wheels and an unusually large sidecover that said "KZ750". These twins are not that rare (I´ve owned 5 of them), you just have to know where to look for help. I highly recommend www.kzrider.com for help. There are more than a dozen twin owners there and a huge number of folks that restore old KZs.