Yep, Neutral Grey for the undersides H. The aircraft is from the 56th Fighter Group, and I think I might have a profile, and maybe a pic of it. I'll check tomorrow, as I'm off to bed now. So far, I've found one gear leg, both wheels, the windscreen and the canopy (for a razorback). I should be able to track down the other leg! I'm guessing the parts will be better than the kits'.
BTW, at that period, only one drop tank would normally be carried, under the fuselage. The paper tanks were silver doped (that stuff again!), and metal tanks painted Neutral Grey. The retaining bands were a dull rust red.
The prop blades would definitely have a 4 inch yellow tip, just over 2mm in 1/48th scale.