I'd try to locate a NOS original asbestos seal, on Ebay or try Langdon's Stovebolt. Also correct installation appears to be an art to get it right so read any tech tips on this you can find.
Best of luck


It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed