The original ZX-14 Gen 1 engine was obviously the 2006. Some slight changes and improvements were then made in 2008. Then came the redesigned 2012 Gen 2 engine.
So your 2006 engine can be replaced with a 2007 to 2011 engine.
From memory the only thing to look out for is a slight increase in header pipe diameter where your slip on pipes fit onto.
See the below link.
2006--->2009 Engine Swap
* Last updated by: yannih on 9/27/2017 @ 4:22 PM *
2012 Metalic Spark Black Kawasaki ZX-14R.
Yoshimura carbon R-77 slip ons,Custom dyno ECU flash,Striker rearsets,Hyperpro RSC steering damper,HM Plus quickshifter,ASV C5 levers,Hel SS transparent red front/rear brake and clutch lines,Kawasaki/MRA vented spoiler screen,Carbon heel guards,R&G radiator guard,Powerbronze carbon rear hugger,ZX-10 front fender with fender extender,Yoshimura frame sliders,M-Factory rear stand stoppers,Escort Redline radar detector,Techspec tank grips and tank protector,Versys 1000 fender eliminator,Kaoko cruise control,Moto red oil cap,Oxford heated grips,Red magnetic oil drain plug,Red and black Bagster Spider rear seat bag (for touring only).