From my experience, this is what I know and do. There are a couple of specific bolts with shoulders on them for line ups. They are required. If you have a known good shifter, and know how to adjust it correctly, then have the correct clips that hold the levers to the pods and bars correctly then you also have a very small adjust play in the side plate which affects the gear shifting. It can cause reverse to go in hard or not at all, and also cause it to jump out of a forward gear. All this will happen with only about a .032 move in the plate. Usually because of a worn out internal part like a fork. But if you were to check this, while the trans was out, you would see what I mean. After playing these cars for 40 years I have learned the little irritations that make people let them go for bargain prices.