hi 101ers

after getting another transmission box for my short frame, i realize that there is a lot of difference with all the box that I've got (5 of them!)some of them have a drain plug at the bottom, and the casing have a different shape, also the selectors inside the tower, one have a key on the shaft with a pin in the center, other have no key and the pin is below the shaft and much larger. Some bush on the shaft are normal bush and others are blind bush. I will download some photos on the " Photos & Videos "

Can someone advise me on the correct transmission please?

regards. Daniel Guillon