Good evening Geoff,
my gut feeling tells me that the zero-tally of the PBJ has rather administrative than military reasons. The USMC Avengers flew fewer missions than the PBJ's but had a tally of 19. I think the PBJ crews were not encouraged by their superiors to submit claims.
By the number of kills that his crew claimed the B-25 top scorer was Ralph Wallace, wasn't he ?
http://forum.12oclockhigh.net/showthread.php?t=50300
Have a good start into the new week,
Michael