A 'deuce-and-a-half', the M35A2 truck (two-and-a-half ton class) designed to carry 5000-pound loads on road but were known to sometimes carry twice as much.
Sounds like your adoptive dad and I were in about the same time period. Where did he have Basic Training? I went to Ft. Polk in Louisiana, talk about culture shock having been born and raised in Southern California.