Jeff, both are sorta available, on the second hand market, at this point. Accurate Miniatures had the Allison engined Mustang as a series, A-36 dive bomber, and cannon and machine gun armed versions. They are out of business, and I don’t know who has the molds currently.
Classic Airframes had the P-51H, and they, too are out of business. E-bay or someone on this site might be able to help. Good luck!