[Mr_Shamrock]

I had the guys at the auto parts store pull boosters for a few different generations and all either were disc/drum set ups or had dual pot drum/drum M/C's. I even found the original thread where someone recommended an early 70's Buick Estate wagon drum/drum set up, but it was a dual pot. I know I could have "Y"d them together or ran separate lines, but I didn't want to do that. I elongated the holes on your bracket to accept the 66 booster and loved the way that looked (nice and tight to the firewall), but finding a way to elongate the rod meant either having to cut and weld a new one or having 2 pivot points on a straight rod which I didn't feel comfortable with. The 66 booster just has a short rod with an eyelet at the end. If it was a threaded fitting there would be many more options.
I know there's a dozen ways to skin a cat I just personally found for retaining the drum brakes, but adding some assist, this way was the easiest. Knowing what I know now it can be done in a couple hours or less too.

Edit: I know I could have swapped out one of the dual pot M/C's for a single and that was going to be option B if this one didn't work as planned.