I agree that headers will help, but they will only give a modest gain. The
alignment pins that are on both ends of the manifold flange are already threaded. Soak for a day with penetrating fluid and turn out with a good vice-grip. Replacing with threaded studs is best. Originally the 3rd and 6th hole from the end have threaded studs. I and others install studs in all eight holes for more even clamping.
If you find a used Clifford intake that doesn't have the water passage, it will work fine except in really cold weather. That's assuming you make sure you have a properly working choke. 292's are generally cold blooded and the heated manifold doesn't help that much.
Many people prefer the Offenhauser 4 bbl intake for the street and they are not heated. Many places such as Summit and Jegs sell the Offy. Clifford sells the Clifford.
Nothing special, but runs well. 23 pages of inline pictures.
http://67-72chevytrucks.com/vboard/s...ht=offenhauser