Oh, wow, can't remember I ever read about this one before. With a complement of 4+8 people and a 105 mm gun, this sure sounds cramped for a 6x6. Though this link speaks only of 7 dismounts, which would still be a regular number for armored infantry:
http://www.military-today.com/artill...ckers_mk11.htm
Any knowledge as to why it failed the bid?