This was a great idea by Chrysler, but the 2 biggest problems were the approaching end of the war, and P&W not sitting on their laurels.
By the end of the war, P&W had successfully tested the R2800 at 3600HP for 250 hours straight with no failures. The P-47 was routinely the fastest piston plane of the war, with an insane climb rate of 4900FPM. This is why P-47's were the choice for buzz-bomb interception.
The other big difference between the Chrysler engine and the R2800 is that P&W radials were well-known to bring pilots home with entire cylinders shot off of the engine. The glycol cooled engines could be completely taken out with one placed shot penetrating any part of the cooling system.
This was expecially important toward the end of the war, when there wasn't much Luftwaffe to shoot down anymore, and P-47s did a LOT of ground attacks. My grandfather told me that when he'd fly in to shoot up ground targets, that there may have been more times he got shot than didn't. The R2800 didn't care. Cylinders missing, no oil pressure, whatever. Just kept chugging along. The whole plane was like that, however. Many came back to the airfield with half a wing missing, rudders gone, tail fins gone, 1 foot holes through the fuselage, whatever.
Most of his air-to-air action was at high-altitudes with the bombers. At the time, the FW-190 was a particularly nasty airplane the Germans were using for bomber interception. The "butcher bird" didn't hold a candle to the P-47. Made plenty of them regret diving through a bomber formation, since the P-47 could out-dive pretty much anything. The first ME-262 jet was killed by a P-47 on a dive attack during a dogfight protecting bombers.