Volkodav - I think a LAV-25, with the middle axle chopped and made into a 6x6, with the Marder 20mm turret would look great!
Frank3k - the rear guns were going to be C5 GPMG's; the same as the Crew Comd and Gunner's weapons. It was the GPMG used by Canadian Infantry Battalions for the time period.
Logan - setting is supposed to be a vehicle purchased in the mid-60's and gone through a second-line upgrade roughly 5 years into its life cycle. So, call it 1969. The upgrade being the addition of crew comd's and air sentry MG mounts, a powered turret in place of the M-113 ACAV style, and Diehl tracks. Toying with the idea that Canada provided an Inf Bn to augment 1 Australian Task Force in Vietnam, or as a UNFICYP vehicle circa 1974.