What numbers do yo have to back up the claim of post-war Allisons being more powerful than the post-war Merlins at high altitude, as well as in 1945? What are the versions in question?
Let's say your numbers here are correct.
How much of a good thing is the perfectly reliable V-1710-39 above France, UK or Belgium in better part of 1942, when compared with a less perfectly reliable Merlin 45?
Or, in 1943, above West Europe or Italy, the perfectly reliable V-1710-81 vs. the less perfectly reliable Merlin 60 series?
You are knocking on the wrong doors there.
Main issue of the V-1710 when initially deployed in ETO was that it lagged behind in power at higher altitudes when compared with Merlin. More seriously, it was also badly out-performed by German engines.
Lack of performance at higher altitudes was due to the low capacity of it's S/C. There was no quick fix for that, Allison was the institution to do it across the pond.
Like I said, we'll have to agree to disagree. I already covered the V-1710-127. It was ready near the end of the war, but the war was all but over. So, no sense in procuring it. Likewise, the Merlin had some nice test stand runners, too, including the RM 17 that put out around 2,600 hp but was never procured for a flying aircraft either.
Stop beating on it, Tomo; we aren't going to agree. Late model V-1710s were performing very nicely at altitude, both with turbos in late P-38s and with the aux-stage supercharger available in general and installed in P-63s that were sent to the USSR. They'd give most warplanes all they could handle if the range was short enough.
Once the P-38J-25 added hydraulic ailerons, the P-38 could have been returned to the ETO with very good results since we also had decent training by then and the faults had been mostly worked out, particularly heaters and intakes. There was no point since the P-51s were doing the job and the P-38s were performing very well where they were. A LOT of the war record for any aircraft depends on timing and military decisions about where they get deployed and how they are used. If P-51s had never been tapped for escort duty, I wonder how many victories they would have had. But, they were, and there's no point "what offing" ourselves to death.
You and I may never agree on the engines, but the course of the war won't change. The Merlin was a great contributor. I just completely disagree with your contention that the Allison wasn't a very good engine and wasn't reliable. It was both once the initial faults had been rectified. It was even suited to the ETO, just not really in single-stage, single-speed configuration. To fight well in the ETO, it needed a turbo or a 2nd-stage supercharger. The U.S.A. was definitely NOT on wartime development push when the war started, and we didn't really start to develop things until after we were drawn into the war. And ... development takes some time. The Merlin was being developed BEFORE the war started, and they did a very good job of it. Allison didn't exactly do a BAD job, but the war was on while they were in early development, and the planes that were deployed early-on weren't really up to the task.
So, do we fight on or give up? The anwer, rather obviously, is fight on and develop as best you can. We did and the results weren't bad. The P-38, P-39, P-40, P-47, P-51, and even the P-63 all served well. Interestingly, 5 of those 6 aircraft started with Allisons. The P-51 obviously moved to the Merlin, but the Allison versions were well suited to what they were used for. The sum of the Allied effort won the war. The U.S.A. didn't win it alone and neither did the British. We both might have lost had the Germans not invaded the Soviet Union, but they DID. In my mind, the Allison played a significant part in our wartime efforts, and it always will.
Was it playing catch-up with the Merlin for most of the war? Yes. But it did catch up and the planes it powered did the job well enough in the end. Their collective war record isn't bad at all. Good enough to win, anyway, when taken together with their other allied counterparts.