Re 38th Armored Infantry Battalion, 7th Armored Division. First, a battalion and regiment are two entirely different animals. When armored divisions were first constituted in the early 1940's, a number of infantry regiments were reorganized and redesignated armored infantry regiments. Regiments were soon determined impractical so all but two were broken up to form individual armored infantry battalions (the remaining two armored infantry regiments were reorganized after the war). The 38th Armored Infantry Battalion was originally an element of 48th Infantry Regiment. I can furnish a complete history for a modest fee.
At your favorite search engine (Lycos, Yahoo, etc.) enter "7th Armored Division". This will bring up 1,140 sites relating to the division with brief references to individual assigned and/or attached elements. One page, < http://hometown.aol.com/dadswar/7ada.htmlhttp://hometown.aol.com/dadswar/7ada.html >, the unofficial page of the division's veteran's association, features an order of battle and brief history of the division. The owner of this site has gathered a selection of official reports into a package which he offers at a very reasonable price.
The division history Turner offers can be found on pages 57 and 58, "Order of Battle, U. S. Army, World War II" by Shelby L. Stanton, commonly called "Stanton's Order of Battle". You can find a copy at any public library. There's a two-line entry for your Dad's battalion on page 269.