Steve,

According to Herb Morrell's book, which was one of my main resources for that article, the first pilot run 88s rolled off the line in late 1945, with the majority being built in 1946. I would think that he would have known, as he was one of the engineers on the 88 project.

June 30th, 1948 is when the Fleetline styling made it's debut. I don't recall anything in Herb's book about which engine block this tractor had, but it is generally accepted that the block without the soft plugs started at the same time. My parts book doesn't give a serial number range for that first block, but an earlier version of the parts book might. So for right now, I can't give you an exact date for the first non soft plug block. Technically, it probably would pre-date June 30th, as they had to build that first Fleetline before then to have it in Battle Creek in time for the big show.

I'll see if I can find anything more specific, but records from that time are almost non-existent.