The 75mm howitzer ammo was approximately 23.5" long. The regular 75mm rounds for the M2 and M3 tank guns was 26.29" long (APC), 26.6" (HE), 26.63 (white phosphorus), and 20.26" (smoke).
So, the answer would be no. Link with some photos:
http://gallery.kitmaker.net/showgallery.php/cat/17894
http://www.usarmymodels.com/AFV%20PH...0Howitzer.html
Cheers
Anthony