I'm not really sure what the shop manuals call for but, I've done a couple of eddie manifolds on 318's, 360's and 360 magnum. Never used anything on them and have not had any issues yet.
Teflon paste or RTV. The bolts are open to the inside of the heads where oil is as cracked mentioned. Over time oil will wick up the threads from capillary action and will end up making little oil puddles on the manifold if sealer isn't used. That oil ends up making a stink, gets burned on and is really hard to clean off.