repair engine 900cc?

my 1985 gpz is broke down, when i was pushing it backwards an obstruction lodged in the chain and apparently buckled, something in the drive mechnism wont engage however, the gears all respond and when i removed the chain tenisoner from the starter motor clutch the cam would not turn over. i've removed the oil pump and trying to avoid an cracking the case .

2. can the transmission of an 1989 jig kawasaki fit in the crank case such as shifting drum and fork .gears with out making any major modifications