Tango, school buses are a whole different animal.
Jason, my COE is a 1 1/2 ton. My '41 was a 1 1/2 ton w/plates.
I've disassembled several different models of 1 1/2 to 2 ton trucks with all different combinations of either rivets, bolts or welds or combinations of all three. Many of which were the same design of 1/2" steel with an angled cut at either end.
Plenty of others I've seen have had frames lengthened so you could hardly tell plus with added plates, some were so mangled it was hard to miss.
Going through the factory specs I haven't seen any documentation to show this was done at the factory. I was hoping someone else could lend their opinions or expertise here.
Jeff