I would use studs. When I rebuild my 23C this winter I'm going to replace the head bolts/studs with all ARP studs. Same with the rod bolts.
http://arp-bolts.com/ American Racing Products. Once you find the length and pitch you can call them to get a match. I've used there products for years in racing engines, wouldn't use anything else. Did you see the price for them @ Jack's? ARP's aren't necessarily cheap either, but you get what you pay for. They will also have the hardened nuts and washers to go with the studs.
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