In the '70's we had a few Autocar's like that running around (tractors pulling gravel-trains, and truck and pup trailer), with most having Cummins turbo 855, or Cat 3406. Saw a few COE Freightliner's pulling trains around Saginaw. But there were MANY K-100 Kenworths, and many GMC Astro 95's pulling gravel trains everywhere in the state. The kenworth's usually had Cat 1693TA or 3406 A/B, or V-12 detroits, and at least an SSHD or 44DS tandems. The Astro's had either 12v71n, 8v92n, or 8v92ta detroits, or 350+ h.p. Cummins, and at least SSHD or 44DS tandems. What few Brockway's I did see were either U360LL dump truck with pup trailer, or U459TL COE tractors with V-12 detroits pulling gravel trains, all with at least SSHD or 44DS.