Does hole in my hood affect cooling? And should I get Hood to rad/hood to cowl seals?

Seal the core support to radiator.
Seal the core support to hood.
Seal any extraneous holes in core support.
Absolutely run a fan shroud making sure the fan blades are tight to the opening and not too far in or out.
Seal the hood scoop opening to everything but carburetor inlet air. Having the scoop opening open to the engine box can and most likely will disrupt air flow through the radiator. Provided the stock radiator is still in good shape, if it did the job before the addition of the hood scoop, chances are, after sealing off the hood scoop opening, it will again, thus negating the need and expense of an aluminum radiator.
Doing the things outlined above will only improve any radiator's performance.