sound's like the 305-478 GMC V-6 canister well the 2QT one any how. . .

mine takes 3/4" wrench I do have 1QT canister that one takes a 5/8" wrench. . .

darn drain plug is 1-1/4" wrench. . .

Mike


1962 GMC K3000, GMC-379 V6.