AMT's Astro in it's original release is most likely a 71 or 72 but could be a 69 to 76. The updated release with the optional fuel tanks and exhaust etc is supposed to be a 77 to 84 so Driptroit 71 and Jim B are quite accurate. Astros were built from 69 to 84 and could of had the same engine options as other trucks.The 3406 Cat was the only Cat offered and all though offered I never seen or heard of one with a KT450 Cummins. Most Astro's I saw over the years had 8v71, 8v71t,6v92,8v92 Detroits or 250,290,335,350 Cummins. The twin turbo 475 Cummins was a short lived engine plagued with problems and was replaced by the 444 which also had issues and was replaced by the 444xl. The 444xl was short lived as it was the test bed for many design features that would become the N14.