The X/YP-37 engine was no longer than than any other C-series Allison, the
exaggerated length appearance is because the turbo-supercharger intercooler
and the engine radiator are installed behind the engine. Thus the requirement
to move the cockpit aft.
... and P&W's R-1830 powered take on a radial engined Hawk 81/P-40, evidently it regularly out flew Merlin powered P-40Fs
stationed at a nearby base:
Drawings of the X/YP-37 and P&W aircraft are on this page:
http://www.wunderwaffe.narod.ru/Magazine/AirWar/52/Draw/index.htmBTW the C-series V-1710 and the AM-35A are very similar in size, with the Allison slightly longer.
V-1710C: L 250.3 cm (98.54 in.), W 74.4 cm (29.29 in.), H 106.4 cm (41.88 in.)
AM-35A: L 240.2 cm (94.57 in.), W 86.6 cm (34.09 in.), H 108.9 cm (42.87 in.)However, the AM-35A, is about 490 pounds heavier at 830 kg(1,829 lbs) vs. 608kg
(1,340 lbs) for the Allison.