Yes, there is a post on ZXF, I believe in the 9R section where there's a company that sells conversion kits. Not sure if it'll work for an 86 ZX-600 though...it will be costly and there's no guarantee it'll make the bike perform any better than the carburetors designed for it.
Case in point. I had the opportunity recently to ride a buddies Triumph 955, an EFI triple. It could have been due to tuning, but my ZX-9R with carburetors was vastly more responsive at the throttle than the EFI bike. That owner even confirmed it, saying what a thrill it was to ride my bike. Amazing throttle response.
So pick your poison. The grass may not be greener on the other side of the fence.