Moroso #26140 is a Distributor Gear Shim Kit that has
(2) .010", (2) .020", & (1) .053" Shims for about $4.
Maybe one from the kit is thinner than the stock shim.
Stock Shim in a 1973 401 Delco Points Dizzy was .032" thick.
Pretty sure the Dizzy gear spring pin is 3/16 dia. x 3/4 long
if you'd want to have extras on hand for if needed.
Assuming your dizzy drive gear end is the same as an earlier Delco.
Recently re-shimmed one to decrease endplay from .072" to .017".