The entire Gen Forum 'site was to have been down today so I tried to e-mail this to you several times. I thought it had gone through at the last attempt but just noticed otherwise while checking my afternoon e-mail. Is "Erik Knudson " your correct e-mail address?
Now, to the matter at hand. Provisional - temporary - units are formed for experimental or training purposes or for specific missions and are, at some later point, either dissolved or made permanent organizations, depending on a number of factors. Such units have no official standing and, therefore, no history or lineage or historical connection to any other unit. When a provisional unit is made permanent, it's officially constituted from the date it became a permanent organization, NOT from the date of its initial organization.
Although the following is, technically, unofficial, I thought you might find it interesting. 43d Division Tank Destroyer Battalion (Provisional) (Light) (Towed) was organized in February 1941 from personnel of the 85th and 86th Infantry Brigades, 68th Field Artillery Brigade, 102d, 103d, 169th and 172d Infantry; 103d, 152d and 192d Field Artillery, 118th Engineers and 118th Medical Regiment. The battalion trained with 43d Infantry Division from its organization to just prior to the division's staging for overseas deployment.
43d Division Tank Destroyer Battalion (Provisional) (Light) (Towed) was reorganized, constituted in the Army of the United States and designated 643d Tank Destroyer Battalion (Light) (Towed) at Camp Blanding, Florida 15 December 1941. Concurrently relieved of assignment to 43d Infantry Division but remained tactically attached until July or August 1942. Departed Boston 5 September 1944 for duty in the European Theater of Operations, arriving in France 15 September. Attached to 3d Armored Division 22-26 December, 82d Airborne Division 4 & 5 January 1945 and 83d Infantry Division 2 February to 9 May. Returned to the U. S. June & July 1945, battalion headquarters arriving at Hampton Roads, Virginia, 5 July. Entire battalion was inactivated 6 November 1945 at Camp San Luis Obispo, California. Decorations: none. Campaign Participation Credits: Rhineland, Ardennes-Alsace and Central Europe. How any of the above applies to someone you're researching depends on his dates of service with the battalion and other factors.