Where to begin?
The Trumpy Razorback is a great kit. A LOT of detail i.e., internal parts that will not be seen once everything is buttoned up, just fun to build though. The fit..... eh. The way you were able to tackle some of the other builds you have shown here, there should be little problem.
The color of 78th FG Thunderbolts. Here is where the fun begins. O.D. Green upper with neutral grey lower is the conventional reasoning. However, I did read an article many years ago in a Fine Scale Modeler magazine, "Special Edition", where a P-47D Razorback "Miss Behave" of the 78 FG was built using British colors for the exterior. R.A.F. Green upper and "Sky" for the lower portion.
All I can say is, have fun, fit twice, glue once, swear, remove part and re-glue. Lastly, best if you listen to someone else, who knows what they are doing .