Morgan,
I can't vouch for all CL 89 Launch trucks-- but the one in the photo you included is a derivative of the basic GMC M135 truck from the early 1950s-60s. This truck was a gasser, had an automatic transmission, and the Canadian Army purchased many of them as their main 2 1/2 ton prime mover to replace the CCKW. As a college student in the 1970's, I used to travel to Bremerton occasionally, and there was a surplus store at Gorst that had a bunch of these Canadian M135s lined up for surplus sales, but they are all gone now. Later, as an Army Officer at Fort Lewis in the early 80s, I saw a few at Yakima the Canadian Army was still using-- all hard cab conversions. You can find more info here, even though the website says they had soft cabs, I believe the one in your photo is a hard cab version, which is all I remember seeing:
http://olive-drab.com/od_mvg_www_deuce_m135.phpThe US Army also had some of these, but for the most part, the Canadian Army was the big user.
VR, Russ