Get a free motor sport magazine, they sell every part and have a photo.,
You can just compare. Im pretty sure your 76 has a R200, the 200 is round and the 180 is thin.
As for gears you have to remove the rear cover and you will find numbers no the gears, if you want to do that there are web sites that will tell you what they mean, I could if you get the cover off, I saved the web site info and would have to look for it.
Terry