English: Riverside Roof tar truck, parked just off Hewitt Avenue near the Snohomish River, Everett, Washington, USA.

I (Joe Mabel) got an email 2010-07-16 from someone who worked using this truck around 2005. He says it is an early 1970s GMC, with a two-stroke Detroit Diesel engine (he thinks it is a 6v-71), and a man named Leonard had modified it considerably. The following is from the email; I've taken the liberty of cleaning up the spelling, and I've left out some passages (marked by ellipses), but this is otherwise verbatim:
"The burners in the tar tank were of his own design, and work better than any other tar truck I have been around. Leonard was famous for this kind of stuff… This tar truck was famous in the industry, and Leonard would use it on every job, even the small ones, when we only needed a couple gallons of tar. … The amount of propane it takes to heat that thing up is very costly. His work ethic, and his love of machines, would not let him do anything else.
"Have you ever heard the sound of a two-stroke diesel?

"The cylinders fire twice as many times as a normal four stroke, so they sound like they are turning fast-- they sound like power. the first time i saw that thing run, I was on a roof top, and this truck came growling up the drive, black smoke coming from the exhaust stack, which had a really neat looking rain cover that banged closed on every bump. Later I learned that this was also of his design. He parked it, and immediately hollered at me, the newest and youngest guy on the crew, to come down and cover the ground underneath it, as it leaked oil badly. I learned later … more about the Detroit Diesel, and how they were notorious for leaking, but from an engineering perspective, that truck was an ugly thing of beauty."