[camerjeff]

It Looks Like you need a new Cam & Cam Followers from the pictures, Luckly they are available again from Kanter.

As for the exhaust manifold, I could see it being repairable if you had the piece that was broken off, but without out that piece I think it is probably no repairable. But I would be happy to be wrong.
1966 Sprint intake & exhaust manifolds are 1 year only parts due to the square flange that the carb heat riser uses (where they bolt together) it is the same shape as the 66-69 1bbl manifolds. The 67-69 Sprint 4 bbl Manifolds have a different shape there, and will not work with you 66 Intake manifold.
So if you find that you exhaust manifold is not repairable, your option are looking for a 1966 only 4bbl exhaust manifold, or replacing you intake and exhaust manifolds with 1967-69 parts.

I do not have any 1966 Manifolds, but I do have a couple 67-69 intake/exhaust manifolds if you decide to go that way.

I did find the Aluminum 1966 front upper & lower Belt covers. and attached pictures. I did look over the pictures you posted and you already have the needed upper rear cover. So it would be $190 USD's plus shipping. The good news it is in better shape than most, there is no wear marks or groove from the water pump pulley.

Unfortunately I did not find any Firebird Motor Mount Brackets, I did find new Firebird rubber motor mounts. If you need them.

Let me know.