NASS Special Blend spec fuel is 10% Nitromethane, 20% Lube (15% Synthetic / 5% Bakers AA Castor), and 70% Racing Methanol.
It's a safe bet Ritch's Brew will be the NATS supplier this year. I placed an order with SIG for St. Louis & Dayton and was told the fuel was backordered TBD.