I'm no expert (typical internet introduction..) but from what I can tell the block 40 D model is nearly identical to the M model. The M model was built from the last production block 30 D birds. A minor engine change and the addition of a factory installed dorsal fin looks to be the only major changes between block 30 and block 40 P-47s.
You should be able to just use the dorsal fin fuselage, add the dive brakes and racks, and I'd think you'd pretty well have it.

Of course if anyone else chimes in with a more worthwhile answer, happily ignore this post. 😉