It is common to seal permanent plugs with JB Weld or equiv. These are usually cross drilled holes to connect to other holes. The passages could not be cast. I have sealed many carbs with JB Weld. Only on the permanent plugs. If those are leaking, consider that. Also keeping in mind what Snazzy said, I wonder if gas tank sealer will work. I have a hunch it's all the same epoxy. On the screw in, I don't advise using any sealer whatsoever. Just the rings. You can email to some carb companies that have online rebuilding videos and they may be kind enough to advise or sell you new copper seals.
1. Mike's Carburetors
http://www.carburetor-parts.com/Copp...er_p_3285.html
2. The Carb Doctor
3. Carbking
Your Stromberg WW Part number is for 60-64 305 C, D, E, 351" ENG, A, B, E, K, L, S, V, 4000 & 5000 SERIES. Walker is a famous old carb parts co. Here is a site with some WW copper washers. Scroll down to about sheet 7 to find G45D and G45C, sold by ID/OD measurement. You will need to measure yours. I don't see how to order except to google their website/find distributors.
http://www.walkerproducts.com/wp-con...l/stromber.pdf
You will also see tons of WW little parts and even aluminum plugs and caps.