The original design used a gun shield taken from the T44 57 mm Gun Motor Carriage, but after the first tests were complete, a new shield was designed with face-hardened steel 5/8 inch thick on the front and 1/4 inch thick on the sides and top. The shield extended over the crew with a relatively low silhouette of only . Experience with the M3 Gun Motor Carriage in the Philippines Campaign, resulted in demountable headlights being used. The T48 was accepted for production in 1942.