Actually, I may be able to help you out myself.
The slot where the mold handles attach varies depending on the vintage of the mold. Early H&G molds have a slot that is ~1/4" wide. Later H&G mods have a slot that is ~5/16" wide.
I have a late model 4 Cavity H&G 68BB from Murphy Oregon that has the early handles, and I have never liked the way the mold flopped around on the handles. I just call Ballisti-cast and ordered a new set of handles ($54) to fit my mold, so I now have an extra set of handles. If you can use them, I'd be happy to sell them. These handles are .253" thick where they attach to the mold.