Your best source for individuals who served with your uncle would be:
43d Infantry Division Association Howard F. Brown, Secretary-Treasurer 150 Lakedell Drive East Greenwich, RI02818-4716 (401)884-7052
During World War II, each infantry division was allotted three regiments of infantry and four battalions of field artillery (three battlions of 105-millimeter howitzers and one battalion of 155-millimeter howitzers). Typically, a battalion of 105's supported a regiment of infantry (the battalion of 155's was general support for the division). Regimental cannon companies were formed later in the war to provide additional supporting fire for the regiment. In many cases, at the discretion of the regimental commander, the cannon company was attached to the artillery battalion supporting the regiment. You might want to ask Harold whether this was the case with your uncle's company. If so, unless your uncle was a forward observer, you'd have a better chance of response from former members of the artillery battalion that supported the 172d than from veterans of the regiment in general. Harold should be able to answer any questions or direct you to someone who can.