Sorry about being a little late weighing in on this; I'm new around these parts, and am just catching up on the various posts.

In my foggy memory, it seems that one of my Chevys had a distributor hold down that was crafted from spring wire about three sixteenths of an inch diameter, and was held down by a stud thru a flat U shaped washer, and a nut and star lock washer. The pointy ends of the clamp were shaped to a sort of modified chisel shape and bore down on the distributor flange, and the thing was slightly bowed; so when it was in place, and tightened down, it bit into the flange, and the spring steel gave with expansion and contraction, and the distributor never strayed from wherever it was clamped. This was not the prettiest thing going, but if polished real nice, and painted, it probably would not look too bad. Like I said, though, my memory is somewhat foggy on this; I may be thinking of something else, altogether.