Well, I appear to have answered my own question with a spot of research. On page 23 of the book "The Debden Warbirds" by Frank Speer it states that the 334th FS changed to QP as it's squadron code on 4 April, 1943 and on 5 April "200-gallon belly tanks were to have been installed on the Thunderbolts, but since they only had 3" ground clearance, they were changed to 100-gallon tanks."
It's my understanding that P-47Cs were not originally plumbed to take belly tanks and it was only after the deeper keels (as seen on the D models) were installed as kits that they were able to carry any under fuselage tanks at all. Given that, it makes converting a razorback D to a C much easier. I stand to be corrected, of course, by the experts here!
My plan (to the extent I have one) is to convert the Trumpeter 1/32 razorback D to a C and use Kits World decals to make Capt. William Smith's P-47C "Little Butch" from spring, '43 to go with my 1/32 B-17F "Memphis Belle". That oughta keep me busy for awhile!