Here's some specifications - I will continue reading to see how many battalions were combat ready-
Crew:5
Combat Weight 46.1 tons
Armament: M3 90mm gun in M67 Mount
Main Gun ammo: 70 rounds (M82 APC, T30E16 HVAP, T33 APBC-T, M71 HE)
Muzzle Velocity: 2650 fps (M82)
Penetration 120mm @30 degrees @ 500 yards (M82 APC)
221mm @30 degrees @500 yards (T30e16 HVAP)
Max Speed: offroads 20mph, Roads 30mph
Maximum effective Range: 21,400 yards
Armor: 115mm gun mantlet, 76mm Turret sides, 100mm hull upper front, 76mm Hull lower front, 50-75mm hull sides
Best described the M-26 in official reports as "not enough action, to late in the war"
They were issued to the Ninth Army and divided between teh 2nd Armored Division (22 tanks) and the 5th Armored division (18 tanks)
So it was combat strength, however with the crippled German Army the M-26 really didn't see enough of the war to be added.
Also it had way to many Mechanical problems that wern't fixed until October of 1945, mainly because it used the same engine as the M4A3 Sherman.
My best guess is it wouldn't be added to the game for the same reason the Meteor wasn't added.