The 1/2 ton / 3/4 ton chassis interchangeability thing is a grey area. Even when I ask vendors who sell 1/2 ton components "will it fit a 3/4 ton truck", they often answer "I don't know"
The assembly manual shows the general differences and the restoration packs include a lot of detail specs that show the differences. Looking at those two resources you'll easily find what you need to know to determine the 1/2-disk conversion kits won't work on the 3/4-ton trucks.
I don't think its a grey area since these kind of issues can all be identified with a little research. When a vendor doesn't know and won't find out or point you to a source of informaion you have to wonder if the vendor cares.
Sometimes you have to do the research yourself. Yesterday at a swap meet I was having trouble identifying a part. I finally bought four of them and carried them to a booth where I knew an expert would school me. It worked, I now understand the identification of that part. I paid $10 for an education and got to keep four examples of the wrong part...
