Remember that the focus was not painting the bellhousing but the engine so the paint could be very thin (overspray) to fairly heavy. Depended on what was near by and the focus of the painting. as well as the angle of the paint gun at the time
An example of a FE bellhousing with engine color on it. Have seen plenty with less that this
I know you will not miss the point that the engine plate and bellhousing attachment hardware were in place at the same time the area got paint
Hope this helps