Replacing Manifold/Stove-Pipe Gaskets

Don't know what gaskets you got, but it is very much worth your while to get the good gaskets for the manifolds-to-head and intake-to-exhaust junctions. For installation tips and techniques, see here and here and here.

Should you replace the exhaust manifold? Well...that depends. If yours is in good shape, not cracked or warped, and the heat riser works and doesn't leak, then that's a good argument for keeping it. But an argument for replacing it is that the '70-'72 exhaust manifolds use an open stove style choke setup, the gasket for which is not available. You can make your own, kinda sorta. The '73-up style exhaust manifold uses a cast choke pocket that requires no gasket, though you'll have to install a different choke thermostat (a number 1233 Electric choke kit would be my pick). If you do go shopping for a new manifold, take your time and shop carefully. All the aftermarket ones are Chinese at price from $110 to over $300. Quality is okeh, usable but not up to factory standards. You will have to spend time grinding away casting flash and slop to have easy access past the runners to install the hardware. New factory Chrysler-made manifolds go by fairly regularly on eBay and they tend to go for reasonable money; that would be the type to get if you are replacing it. Or you could take the opportunity to upgrade and prevent future manifold breakage by installing Dutra Duals. :-D