Shoebox: I have been using a set screw and a" spacer collar for height)"for the last 20 years. My distributor is a Mallory but, I bet it would work on your chevy. Look at post #5 in this thread.
https://www.fordbarn.com/forum/showt...tor+hold+clamp
Also, do a Fordbarn SEARCH on Distributor hold down or distributor clamp.