From Wikipedia...
P-63D One aircraft (43-11718) powered by an Allison V-1710-109 (E22) 1,425 hp (1,063 kW) featured a 10 in (25 cm) wingspan increase (to 39 ft 2 in (11.94 m), gross area being increased to 255 sq ft (23.7 m2) and, most noticeably, a rearward-sliding bubble canopy. The series was cancelled in 1945.
When trying to identify any U.S. military aircraft, I strongly suggest to Google both the serial number (in quotes) and "Joe Baugher". Most of the time it will take you to his detailed lists or his articles, both of which are among the very best resources you can find online. In this case, the first result was the following...
http://www.joebaugher.com/usaf_fighters/p63_6.html