EGR, is it necessary?

Assuming you are switching it up to a carb manifold etc, then no it is not needed. Mopars did't get egr till the 70's.

The alum manifold will probalby be threaded so pipe plugs can be put in where the valve would go.

If you are planning on doing something exotic, like switching in the EFI too, you are better off to leave it in. The computer won't run any better without it, unless you have the mean of somekind of radical reflash.