The wing on the B was thinner...that is the reason the guns were mounted at an angle -- which caused jamming under G. The D wing was thicker to accomodate the guns being mounted upright.
That would not be the case.
The wing from WS 61.5 all the way to the tip was EXACTLY the same in every design feature save banked .50's versus upright 50's (in P-51D and H) and 20mm (in the P-51) in an earlier model. To accomodate the upright guns for the D required a gun bay change in mounting brackets, adding an extra link/case chute and modify the ammo storage section - but not a 'fatter' wing.
In summary - both B and D wings had the NAA/NACA 45-100 modified Laminar flow wing and every dimension save for the area where the D extended the root chord to accomodate the more swept Strake (from CL to 61.5 for leading edge only - but the inside/outside dimensions outboard of 61.5 (where the guns were) is the same and the airfoil contours were the same.
You may (or may not) know that the prototype D's were two P-51B-10NA's pulled off the line - they actually had and kept the P-51B 'shallow strake' and wheel design but USAAF would never agree to stopping production to re-design (and re-tool) a completely different wing.
The P-51H had a different wing altogether.