muffler bearings / obligatory

if you are talking about that 3/8" line on the left side of the pic it's just a bowl vent hose IIRC.

not necessary i dont think

If that engine was a Camaro , this question would have been answered here before you hit the post key.

Antifreeze intake supply :evil:

Ok, so I've got a couple of other pics. Jasonsauto, it's not the 3/8 one you mentioned, but the one just to the right of it. It looks like it comes out of the vacuum advance of the distributor. Next question is, as you see in the second pic, the new carb doesn't have that port, but rather some sort of vacuum device (the round siver piece) that doesn't have a port. Do I need another distributor now?

I’d be highly surprised if your new Holley doesn’t have a vacuum advance port. Might be in a different location but it should still have one.
If it doesn't it’s not that difficult to modify a distributor for mechanical only advance. It’s just basically a change of springs so the advance weights swing out faster.