F4U's 1st combat was at Valentine's day of 1943, curiously enough they (along with P-38s) got a bit spanked, with 3 Zeros claimed for 10 American A/C lost.
P-51 is already in production, just cancel the darned A-36 and produce actual fighters. The P-51B happened because 2-stage supercharged Merlin offered excellent power at any altitude, and especially high up, year or two before the V-1710 was ready to emulate that. 1st contract for such P-51s was signed at July 25th 1942 - about a year before USAAF started the escort panic.
The increased weight of the V-1650-3 was compensated by using a bigger cooling system installed aft the CoG, that also included the intercooler radiator. No major screwing of the CoG, the Britsh 'Merlin Mustangs' flew without fuselage tanks without problems, as did the initial P-51Bs. CoG was screwed with fuselage tank holding more than 40-45 gals, such outfitted Mustangs were supposed to enter combat with fuselage tank empty.
Installation of the V-1650-1 means there is no intercooler (= easier job), and engine is some 150 lbs lighter than the V-1650-3.
If USAF is that much afraid of F4U, ship them to the RAF and RCAF units in the UK.