Remove a valve cover and ID the cylinder head casting number.
Its between the valve springs on the top of the head.
With This I'll tell you what plugs to install.
Engines with a non stock cam with increased duration and overlap
show less manifold vacuum at idle.
Such engines also want an increase in the spark advance at idle.
They run much much better when the distributor mechanical and vacuum advance curves are recurved to suit the non stock performance cam.
Spark plug gap will be .035" reguardless of points or HEI.