65 Barracuda Disc Brake Conversion Help Needed

According to PST and Wilwood they didn't have any record of there being a difference between the 73+ disc/drum spindle. I asked specifically about that. It was a concern of mine as I was going to get thier 2" drop spindles to be done with all this. They said it would work on the 74 duser drum spindle. Are they wrong?