In 1946, he piloted the Koopman Offenhauser and finished 4th in BSMRA points, competing at tracks from Seekonk, Massachusetts, to Akron, Ohio.
In 1948, Sostilio finished sixth in United Car Owners Association points, driving for the MacLeod Racing Team with Johnny Thomson.
In 1949, Sostilio turned his focus to stockcar racing, traveling from New England to South Bend, Indiana, for three consecutive weeks and winning the trophy each time.
In AAA competition, Sostilio won seven races between 1948 and 1950 at tracks in South Bend], Akron, Miami, and Heidelberg, Pennsylvania.
In the early 1950s, Sostillo competed in the AAA Big Cars alongside his teammate, Indianapolis 500 winner Johnnie Parsons.