Joseph,
I'm wondering about this.......
I have a Corvette article that featured the BBC engine 
assembly process at Tonawnnda.  Painting was also covered.
This is a much debated topic on the NCRS technical forum.
Verne probably also saw this on that site some time ago.
I have a photo showing the BBC's coming down the paint
line and the bell housings are clearly installed.  Unfortunately,
the photo is in B&W so it's almost impossible to tell for
sure. Why you have several '621 bell housings w/o paint is
a mystery to me.  I do know that the painting process was very 
subjective, depending on the person actually painting.  This
is clearly evident from the different levels of overspray
found on original cars.
I have a '621 bell housing that came off an original L/71
'69 Vette and it has orange overspray all around the perimeter 
of the housing ( where it mates against the block ).  
I bought it from the original owner because of this
original paint scheme.  BTW, it also has its original 
yellow crayon inspection mark over the orange paint.
I wonder if painting was bypassed on certain days due to
personnel availability or production pressures.  Some
engines I have seen sure look like they were never painted. 
 
BTW, I have an invitation from GM to visit their historical
archives for research purposes.  Engine painting was one of
the topics I had planned to look into.  Time is my problem.
Steve 
