I just finished the study on the 20th, 55th, 364th and 479th as they were only P-38 groups to convert to Mustangs. Some really suprising results statistically. I used USAF 85 and Kent Miller's "Fighter Units and pilots of 8th AF. They don't correlate 100% on awards but are pretty close, particularly on air awards.
Ther is judgement on Cause of Loss. If a guy went down for unknown reasons near an air battle - I assigned air to air. If he hit the ground strafing an airfield I assigned 'flak' to differentiate from an engine prob, etc.. so possibly the air to air and air to ground Losses are slightly overstated for both the 51 and the 38 - meaning the ratios will be conservative (lower)
The first P-38 units converted to Mustangs from late July (20, 55 and 364) to late September (479). The longest span of combat ops was 55th FG from Sep 43 through Jul 44. The shortest was May 44 through Sept 28 44... and it was best performer (I suspect Zemke was the difference)
Here is the aggragate result
P-38
awards = 278.6 air, 133 ground ----
losses = 101.0 air, 106 ground ----
P-38 award to Loss Ratio = 2.75:1 air, 1.26:1 ground
When these guys converted to Mustangs to finish the war
P-51
awards = 661.5 air, 790 ground
losses = 44 air, 119 ground
P-51 ratios (from converted P-38 groups) = 15:1 air, 6.63:1 ground.
I suspect the ridiculous air ratios of the new Mustang drivers had a lot to do with rapidly shrinking LW quality - while the early 38 drivers had their hands full with Allisons and Messerschmidts..
Some interesting and puzzling 'stuff'
1. In general the Ops/Acc losses in P-38 groups are slightly less than the flak losses while strafing.
2. In general the Ops/Acc losses in P-51 groups are slightly more than the flak losses - implying that maybe that second engine was useful.
3. When the Mustang Groups were going wild destroying a/c on the ground in March and April 1944, the P-38 groups were barely scoring - but losing a lot of guys to flak. The 55th only scored 7-5 through July! while losing 25 to flak.
4. The 479th was head and shoulders above the other 3 in holding its own in the P-38 with only 4 losses air to air in getting its 52 awards - just barely improving in the Mustang.
5. As near as I can tell the P-38s shot down 5.4% of total 8AF FC while losing 16% of losses air to air.. This had a lot more to do with Doolitle's decision than 2x price.
I wish the MTO data was better - it is clear that the P-38 was much better in MTO than ETO.
I am in process of dissecting the P-47 ratios in a similar manner plus making some corrections and will post when complete.