Outside of an extreme case of good fortune, where you find an uncracked, unrusted replacement manifold from a salvage yard, your best bet for a leak-free exhaust experience is to purchase Tom Langdon's Stovebolt exhaust headers. They're made for the 230-250-292 series straight six engines. Tom's link is
http://www.stoveboltengineco.com They don't come cheap, but then again nothing unique and of quality does. Will cost you around $300 once you add in shipping and the price of his header installation kit.
There are other options. Clifford Performance makes short tube headers for your engine. I have a set in my garage. They're a great quality product. Both Hedman and Dynomax makes tube headers specifically for your application (1963-79 Chevy truck w/230-292 6 cylinder engines). I have a set of the Dynomax headers on my 66 stepside with a 292. Clears everything great and about half the cost of the Stovebolts.
The factory cast iron manifold is no longer available OEM through GM (I checked already) and occasionally an exhaust manifold appears on Ebay. If it's an OEM on Ebay it won't go cheap. Check out this 292 manifold that some idiot paid $290.00 for!!!
http://cgi.ebay.com/ebaymotors/ws/e...1&category=34203&item=2434927737 -ftyler
