Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Well Allison did develop an auxillery supercharger stage. It was similar in configuration to the 2-stage superchargers used on the P&W R-1830 and R-2800 engines. These were most notably used on the P-63 series of fighters. (albeit early models lacked an intercooler, though some were fitted with water injection, like on the P-63C)
I realize that Allison had created this configuration with the external supercharger, but from what I have read, the USAAF had problems with these in the later model F-82s and these were slower than the earlier F-82s using the Merlins.
It would have been interesting if Allison could have developed the V-1710-127 further. From what I have read, the temperature from the turbocompounding was extremely high and the metallurgy capable of handling these temperatures were not available at this time. Here is an excerpt from Wikipedia about the engine..
"The most powerful factory variant was the V-1710-127, designed to produce 2,900 hp (2,200 kW) at low altitude and 1,550 hp (1,160 kW) at 29,000 feet (8,800 m). This engine was static tested at 2,800 hp (2,100 kW) and was planned for installation in an XP-63H aircraft. The end of the war ended this development, so this promising experiment never flew. The extra power of this version was derived from using exhaust turbines, not to drive a turbosupercharger, but to return that energy to turning the crankshaft. This was called a "turbo-compound" arrangement."
Although the Conqueror accounted for 2/3 of the Army's purchases of of large engines as late as 1932, the Conqueror marked the beginning of the end for Curtiss aircraft engines. Tests in 1931 showed glycol leaks and, with a declining interest in liquid-cooling, funding was cut a year later.