You're setting yourself up for aggravation if you use a '70-'72 exhaust manifold. Its open-stove choke setup is a pain even with factory parts (leak-prone gasket no longer available; homemade solutions leak worse). That's on top of the other issues with old exhaust manifolds (warp, crack, busted heat valve, etc). Do yourself a favour and get a carefully-chosen new exhaust manifold. Manifold stud & nut info in this thread. Also, it is very much worth your while to get the good gaskets for the manifolds-to-head and intake-to-exhaust junctions. Then save yourself a bunch more aggro and get a № 1232 electric choke kit—works way better than the factory 2bbl choke thermostat, and it's adjustable (the factory item isn't).
