The 266th were part of the 66th Inf Div, so your information is correct. This brief history was provided:
Brief History of the 66th “Black Panther” Division as prefaced by Philip M. Coons in “Letters Home”
The 66th Division was activated on April 15, 1943 at Camp Blanding, Fl. Its commander, Major General Herman F. Kramer, continued with the division until August 1945, when he was relieved by Major General Walter F. Lauer. General Lauer commanded the division until its deactivation in November 1945. The 66th Division was part of the Sixth Army Group and participated in the Northern France campaign.
The division was formed and had its initial three months of training at Camp Blanding in northeastern Florida. The division then moved to Camp Joseph Robinson near Little Rock, Arkansas for further training. They completed their training at Camp Rucker, Alabama. In November 1944 the division arrived at Camp Shanks, New Jersey, its final stop before being shipped overseas. Part of the division sailed for England on November 15, 1944 aboard the George Washington and the George O. Squier and the rest of the division sailed on the HMS Britannic on December 1, 1944. While in England the division was billeted in small towns and barracks at Camp Blandford in the County of Dorset on the southern coast of England.
The 66th Division consisted of the following units: 262nd , 263rd, and 264th Infantry Regiments, Headquarters Battery, 721st, 870th, 871st, and 872nd, Field Artillery Battalions, 266th Engineer Combat Battalion, the 366th Medical Battalion, 66th Counter Intelligence Corps Detachment, 66th Quartermaster Company, 66th Cavalry Reconnaissance Troop, the 566th Signal Company, and Headquarters Special Troops, including a Headquarters Company and a Military Police Platoon.
The 66th Division crossed the English Channel on Christmas Eve 1944. The majority of the infantry troops were on board the SS Leopoldville and the HMS Cheshire. Just five miles off shore from Cherbourg, the SS Leopoldville was torpedoed by a German U-boat. Fourteen officers and seven hundred forty-eight servicemen were lost.
After arriving at Cherbourg the 66th Division regrouped and headed for the L’Orient and St. Nazaire sectors in Brittany to relive the 94th Division which had been guarding the German submarine base pockets that were left after the D-Day invasion. Estimates of the number of German forces left behind in these pockets ran from fifty to one hundred thousand. The 94th division was sent to the Battle of the Bulge. While in Brittany the 66th Division carried out daily reconnaissance patrols along the one hundred and twelve mile front and conducted periodical artillery fire on the pockets of resistance. The artillery fire disabled a number of big German guns and sank numerous re-supply boats. Upon the German surrender on May 8, 1945, the 66th Division moved to the area near Koblenz, Germany for occupation duty and to guard German POW camps.
In late May1945 the 66th Division moved again, this time to the Marseille area on the southern coast of France to staff the staging areas in Marseille, Arles, and St. Victoret from which troops were being sent to the war in the Pacific. Once situated near Marseille, the 263rd staffed the St. Victoret staging area and the 262nd and 264th staffed the Arles staging area. The 870th was assigned as an MP unit, the 871st guarded the Miramas Depot, and the 872nd was stationed in Marseille. The 721st became a transportation unit. The 266th Engineer and 366th Medical battalions performed their usual duties. While in the Marseille area the 66th Division constructed a total of eight outdoor motion picture amphitheaters where the GIs were treated to numerous USO shows. Many 66th Division athletic teams played on another on newly constructed athletic fields.
With the cessation of hostilities in the Pacific a small part of 66th Division sailed for home in late October 1945. The remainder of the men in the 66th Division who did not have enough points to return home was either sent to Delta Base in southern France or to Germany and Austria to serve as occupation forces.
Overall the 66th Division suffered the following casualties: 804 killed, 268 wounded, seven missing, and nineteen captured. There were 1,098 battle casualties and 849 non-battle casualties.
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Here is a Senate Resolution recognizing the 66th Inf Div
I would strongly suggest that you contact NARA in Maryland, for they hold unit records that have been declassified. This is where I obtained all the info on my father's unit. Each unit will differ, but most have daily, weekly and monthly journals, including after-action reports for the battles.
It could very well be that whoever compiled the info for you, was in error. That does happen from time to time. I look forward to hearing from you.