The transmission that came with my 1974 GTV had a broken drive gear assembly. (I am unsure what vintage the transmission is) I took it out to find there was no gear on the shaft at all. I located a suitable (I thought) replacement. I finally came to swapping it in and have encountered difficulty. The transmission is out of the car and I placed it in gear to rotate the output shaft and tried to insert the assembly into the hole but it appears to bind. I am not comfortable applying too much force to it. It does not seem to want to mesh. Are there possibly different gears in terms of tooth count? Or are the internal gear and gear count on the assembly a matched set?? Any help is greatly appreciated.