Sorry, I thought everybody knew the monkey. It's a 65 GT350, 5S275. However, after I wrote this post yesterday and gone to bed, I took a look in the 1965 Mustang Body Assembly Manual and there it was. Bottom right corner on page 53 there is a picture and text saying the following under #9 : (ESB-M62J5-A-1724-B) Black Out Paint - Applied to entire surface of air extractor depression, see figure 1.
Don't know, of course, if this applies to the SJ plant but it makes sense as it looks very odd
with white under one screen and black on the rest. I know, Jim Cowles and I discussed this some years ago when he asked how my car was in this area. I told him mine was white and after that time I haven't thought about until I visited a friend who just got his 65 GT350 back from the paint shop when I noticed this odd look and asked if he knew about this. He didn't so I told him I will ask the experts.
Thanks,
Texas Swede