The cut on the fender just says that the truck started life as a N/A engine. The early M35A2's were N/A and had the exh out between the passenger side duals and had the LD465 When they were converted to the LDT465, the fender was cut for the stack. The M35A1 had the LDS427-2 and had a low exh. The M35's were dual wheeled M34 trucks and had the OA331 gasser in them. Gasser fenders are much different than LDS, LT, LDT fenders.
Hole has a 1954 Reo. It started life as a gasser, this is known because of the bolted in rt. rear motor mount. The factory multis had a rivited in rt. rear mount and, in the early 50's, the multi wasn't in service yet. The fenders were changed to the "diesel" type. His truck also had a complete depot OVH in the early 90's as evident from the hand stamped data plates. Carnac was able to give the original mfg date by a brass tag, wire tied to the drivers side loop on the frame.
So, judging by his truck, the gasser M35's WERE upgraded to at least M35A2 series trucks as late as 1990. But, his truck could have been repowered/upgraded earlier and just depot OVH'd in the early 90's with another multi.