Seems to me the way the P-39D is modeled is quite... "generous"... and that it has very few flaws compared to some later planes.
Were it forced to go up against 109Fs it historically would be owned, but in AH would probably more than hold its own. The P-40E we have is really a P-40K (flight model) and the B-25 will soak up 700+ 7mm hits all in a localized area without destruction. I caught one in an FSO asleep at the wheel in my a6m2, unloaded most of my 7mms into him in steady flight at close range and nothing. Ack got him before I did.
I think the allies would have the upper hand on this one.
Definitely would be interesting to see something worked up. However, at the time of the invasion there were no lend-lease planes. Most were woefully obsolete spanish civil war planes, biplanes, etc. Thousands upon thousands were destroyed in the opening days. Now, if you get into the time where lend-lease planes are common, you've got improved LW rides in the air. Depending on the time frame, 190a-5s could be used, as well as the 109G-2 and if you push it into 1943, the 110g2 and 109g6. The 4x20mm guns on the 190a5 would be MUCH more effective at downing iron dogs (p-39s) and iron-like bombers (b-25s) than the single 20mm in the 109F.