I've had many of those trucks over the years. It looks to me to be a WM series truck. W being civilian cab, M being military frame ( straight like a ladder,no arches to frame at suspension) Other ex-military items used with those frames are divorced mount t-cases, pto driven winch and industrial versions off engines . Low compression to idle all day and reverse flow water cooling. Water goes from cylinder heads to rad. Commonly seen in dump trucks of that era.Original front diff should have dana 70 with pucks instead of outer u-joints. Mine was a WM375 with duallys. Toughest truck around the local river hole here for years. Had a 20 ton tulsa pto winch. 361 industrial w/ 5 speed. Retired it (sold) due to yearly brake jobs required. Very poor brakes. 13 x 1.75 shoes. Get all the extra parts cause you will need them. As evident by his collecting them.