[3] The chassis revisions resulted in a car roughly 22 mm (0.87 in) wider than the TR4, although length and height were unaffected.

There is also a new piece of chrome trim on the side, starting near the rear edge of the door and ending at the front of the car with integrated signal/marker lights, which were moved from their earlier position in the corners of the grille.

New smaller front bumpers and a convertible top patterned after the one from the Herald complete the exterior differences.

In response to requests from United States distributors Bud Forman and Les Genser,[5] Triumph developed a version of the TR4A fitted with a TR4-style rear live axle and made IRS an extra-cost option for the US market.

Even though the SCCA declined to homologate the TR4A in 1965, Kas Kastner, Triumph's US Competition Manager, and his modified "Super Stock" TR4A won the D-modified National Championship in 1965 at Daytona with driver Charlie Gates.

[7] Bob Tullius' Group 44 and others successfully campaigned these cars during the 1965 to 1973 seasons, accumulating a respectable collection of finishes.

In the United States, price pressure and tighter emissions standards resulted in a less powerful but otherwise identical car fitted with twin Zenith-Stromberg carburetters, called the TR250.