Most of the old Internationals had Red Diamond engines, became the International line as they bought Red Diamond out. Thus the RD engine series as was explained to me decades ago.
Well I got bored today and did a bit of research, the KB-12 and KB-14 models were available with Continental 6586 engines, 587 cubes giving 200HP at 2600 RPM. Two cylinder heads and tall rocker covers. I have worked with RD 450 and 501 engines in the past and do remember that truck not having the shallow one piece rocker cover. But at the age of 9 or 10 I was just shadowing my Uncle that seemed to do all the truck work at that time. He did have a military maintenance background and it's entirely possible he did swap a 6602 in there for the 20 extra horses.
This was all in the late 60's, I remember 1/4 turn valves in the cab to supply trailer air, a huge Johnson bar park brake (no maxis), I think the truck had a 5x3 trans and the interlock was a lever between your heels, pretty crude by todays standards.
It seemed like the gooseneck on the old peerless 3 axle lowboy was nearly as tall as the cab on the old KB.