Dave,
GM never put a V-12 in the '66 and up Long Nose 9500's.
According to Jolly's site, V-12's were only available in the B-, BW-, L-, & LW-7000 series trucks.
I know what you are thinking tho, as it stands to reason that a "Long" engine should go in a "Long Nose" truck, but to fit them in the above trucks, they had a larger "Dog House" inside.
There are some pictures of a "B" Model GMC with a V-12 from the Winchester show and I'm sure there are some pictures around of the L-Model with one, but I just don't have those links handy right quick. Maybe someone will jump in with some for you.
Bill
