I have just cleaned and sandblasted my bell housing. DOes anyone know what color they where from the factory?? ( I have black and yellow paint)

Or is it left and natural steel finish?

I believe they were unpainted from the factory.  If you're looking to be concours correct, buy some "cast blast" paint from one of the specialty places.  If not concours, paint it the color you want, it's your vehicle.

John - "The Hoosier Hurricane"

http://www.ford-trucks.com/user_gallery/displayimage.php?&photoid=66455&width=0

If you look closely, you can see a yellow bellhousing. I have personally seen yellow paint on a 1956 bellhousing.

1959 and 1960 f-100sAkron OH

Oops!  I spoke out of turn.  I was thinking passenger car, didn't notice the truck in your avatar.  I don't know about painted bellhousings in trucks.  Sorry.

John - "The Hoosier Hurricane"