He was declared the National Boxing Association Featherweight Championship of the World on May 1, 1940, two weeks prior to winning a sixth-round technical knockout over Frankie Covelli on May 15, 1940.

The NBA had withdrawn the world featherweight championship from Joey Archibald the previous month for his refusal to fight leading contenders, including Scalzo.

[6] At the end of his amateur career in 1936, he won the New York Daily News Golden Gloves Open Bantamweight 118 pound Championship before a crowd of 20,000, and soon decided to turn professional.

The bout was not a title fight, and certainly not recognized as one by the National Boxing Association (NBA), a sanctioning body with a wider range and more prestige than the NYSAC.

[8][2][9][10] Demonstrating his punching ability, Scalzo defeated Lou Transparenti at Turners Arena in Washington in a seventh-round technical knockout on January 3, 1939.

[11] On May 15, 1940, Scalzo defeated Frankie Covelli for the National Boxing Association (NBA) World featherweight title at Washington D.C.'s Griffith Stadium in a decisive sixth-round TKO.

[1] On July 10, 1940, in one of his few defenses of the world featherweight title, Scalzo defeated Bobby "Poison" Ivy in a fifteen-round TKO in Hartford, Connecticut.

Scalzo showed superiority in both long range boxing and infighting, though in the twelfth, Ivy staged a comeback which brought the Connecticut crowd of 5,000 to their feet.

[14][15] On July 15, 1940, Scalzo defeated Maxie Fisher before a crowd of around 5600 in a ten-round points decision at Meadowbrook Bowl in Newark, New Jersey.

[2][16][17][18] On August 26, 1940, Scalzo defeated Jimmy Perrin in a well publicized ten round unanimous decision which brought 10,000 fans to City Park Stadium in New Orleans.

[20][21] In an unexpected loss, on October 4, 1940, Jewish boxer Julie Kogon defeated Scalzo in a non-title eight round points decision at Madison Square Garden.

[2] On April 18, 1941, he won a first-round technical knockout against Andy Strivani at Legion Stadium in Hollywood, flooring him four times in the first round with rousing rights to the head.

[2] On July 1, 1941 Scalzo lost the NBA world featherweight title before a near capacity crowd of 9,500 to Richie Lemos in a fifth-round knockout of a 12-round bout at the Olympic Auditorium in Los Angeles.

[26] Scalzo's last publicized fight was against reigning NYSAC and Pennsylvania lightweight champion Bob Montgomery on October 25, 1943 at Convention Hall in Philadelphia.

Though Scalzo was an ethnic Italian, his comic skits with Addie often presented him as owner of a Greek restaurant and were performed at such venues as Boxing Guild meetings and honorary dinners.