The early k11 1.0 boxes with the 160mm clutch fit the k10 driveshafts and such and also fit onto a cg13. So thats not an issue. Im not sure about motor mounts but you need to sort out the wiring loom. (not to hard, use a early non nats ecu) and fueling. The k10 is carbed and uses a mechanical fuel pump with only 1 line coming from the tank. a k11 uses a electric pump and fuel injection and also has a fuel return. So you need to either use a figaro tank (or was it pao?) or make something to have a return into the tank. Or fit a set of carbs to the k11 engine. And ofcourse standard stuff like fit up the exhaust.
Its shouldnt really be a hard swap if youre somewhat handy.