For sure a heavy truck engine. From what I have found the 331 is just two clicks below the 413 and appears to have the same outside dimensions. The in between is 376.9. They all use the same size bearings. The 331 has a 3 3/4 bore and a 5" stroke. 280 ft lbs at 1600 rpms. It would be legal in the FX classes.
Some 413 specs:
Bore& Stroke 4 1/16 X 5 5/16
413 ci
171 hp @ 3,200 rmp
424 ft. lbs. @ 1,200 rpm
8.5 to 1 CR
12 ports
head 9" X 30: 33 studs
Overall length Dampener to trans 48"
Bell housing to timing cove surface 33 3/4"
Pan sump to top of carbs 34"
