Tomo, can we include Continental's proposed H-2860, which was derived from their I-1430 engine?
Why not.
The 16 cyl derivative might've been called the H-1900 (= 1430 x 1.33). As noted by
S
Shortround6
above, the individual cylinders might be a liability, and the valvetrain will need to be updated. If we accept the 1300-1350 HP power as realistic for the I-1430, the H-1900 should've been making around 1750 HP military power. 2000 HP WER if the cylinders are okay with this; dry weight - 950 kg? P-40 and P-51 should've been interesting with these,
if the engine matures in a timely manner.
Allison H-2260 (ie. 1710 x 1.33) - 1500-2000 HP military/TO power, 2000-2100 HP WER, 2400 with ADI? Might be a good fit to a P-47/-72 (= have "Fisher body division" make these instead of the P-75?), B-29, B-25/-26, A-26 (yes, I know that USAAF was not keen on liquid cooled engines on the 'attack' aircraft category).
Similar story with the 16-cyl H-2200 by Chrysler.
'Target weight' of a bit above 1000 kg?
For the British - the Merlin-based H16 engine instead of the Vulture should've been a very interesting and useful engine. Talk mimicking the H-2200/2260 in shape, size and weight, for installation on the Typhoon/Tempest, and a slew of FAA aircraft (Fulmar might be too early for this, but Barracuda, Firefly and Sea Fury might match the timing). A bit better power than the US competition in the same period, due to the Merlin's timing and genes?
The not-Sabre - perhaps Napier going for an 'square' engine (= bore equal to the stroke) for a more compact and higher revving engine?
'Target weight' of ~1100 kg (ie. similar as the Vulture and Sabre)?