Mine is a stock points distributor from 1966. I have a new big block in the works. I run without it at the moment. It doesn't get much use working 6 days a week so it sits..I think that you could replace the canister or distributor.
I found out with mind that the vacuum advance was shot on my distributor. And was popping thru the exhaust. Motor was shaking at idle so I pulled hose off distributor and the shake went away..my 002
On my 383 my thermostat housing was leaking.. filed it smooth new gasket silicone still leaked.. found the bolts were bottoming out added 2 washers problem solved...
I also had this issue between timing cover and block. The metal gasket rots away. Could be they didn't put sealer on the bolts going into water jacket...