I lucked on to a website that had the answer. The first 1,000 or so -5's had the window and they removed it for the remaining main build. That appears to me that the -3 would have all had them.
Now for the next question. There was a small "hump" on some cowls right before the exhaust...
I see many differences in pics of these two Hellcat versions. The -3 and the -5 had different canopy frames in front but I see windows behind the main sliding section (in fuselage behind) on some and not on others. Were these windows based on the -3 or -5 version or were they due to some other...