Why are you trying to put 800 eccentric in 750 you can use the wheel from 800 for that
Long time ago I had the blueprint for where the reliefs need to be cut into the 800 wheel. Isn't just a strait buy and bolt on.
Also, the entire assembly not only looks different, but has a different brake setup as well. Who knows what the point really was of this ancient thread, but, it was probably worth asking if there is some pile of parts in a shed somewhere that might save some money if it is all compatible.