Try this:
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Here is a great one-piece gasket and studs kit for 235/261, that works really well without any leaks. The gasket is really thick.

http://www.merchantamerica.com/chevyhotrod6/index.php?ba=product_enlarge&product=57209

The owner is a well known and knowledgeable builder, who can make just about anything.
Great to talk to over the phone. It worked great for me!!!