I doubt length of the tail shaft is the problem...more likely the number of splines if its an import box with the clutch slave on the driver side. if its the original box and shaft out of the car it will fit without any adaptation unless you have cut and rewelded the engine mounts ( I dont know why youd do that as the gze will fit in there the same as a C ).
oops just realised I missed the bit about the auto being in thoer originally..its the number of splines which will be the problem...go buy a new tail shaft is the cheapest answer.