Yesterday my son whipped up a pair of cutout block off plates for me out of 3/16” steel. These will stay in the glove box in case the cutouts ever get stuck open away from home:
I’m going to paint the outside faces with the same POR-15 exhaust manifold paint I used on the manifolds and coat the inside with WD-40 and carry them in a plastic bag.
I don’t really want paint on the inner surfaces as it may gunk up my copper gaskets if the caps are ever pressed into service.