Offhand, I don't believe MTH has ever produced an N&W class A in Railking. They have done in the Railking line the J, the Y6, 0-8-0s and 4-6-2s in N&W but I've never seen an A.
Funny enough, MTH has made the A in their Premier line in every known variation.
Lionel did make a Lionmaster Class A, in both TMCC and Legacy though if you have your heart set on an A that can make O31 curves.