Hi Patrick,
Small block engines were painted with the bell housing in place. There was however, no attempt to paint the bell housing itself, or to protect the housing from getting paint on it. So the majority of the housing is natural aluminum. There was usually a band of orange over-spray about 4" wide on the portion of the bell housing that bolts to the rear of the engine block.
Many people find this looks pretty sloppy so most times only people who are doing a 'factory' type restoration do the over-spray, with many people leaving the entire housing natural aluminium
Regards,
Alan