The 302 GMC is a highly sought after motor. The casting number is a later "Civillian" 302. The 302 motor will bolt into any 1939 to 1959 gmc. However being the later civillian 302, this motor has "side mounts" in the front. To bolt it into a 1939-1955.1 gmc truck, the front timing plate needs to be swapped.
The 302 is full oil pressure as is the 228, 236, 248, 256, and 270 gmc motors used from 1939-1959. The gmc family of motors is about 2 inches longer than the chevy 216, 235, and 261 motors. Factory HP numbers are only about 160 HP. There are many speed parts avaialable for more performance. 225-275 hp is not unheard of on a streetable 302 motor.
I brought my 302 to an ATHS show for it's first start. Jim Carter of Jim Carter's truck parts came running over to see it as I pulled up. He wrote this article on my motor.
http://www.jimcartertruckparts.com/Showcase/the_king.php
