Bob - yep, mistook some stamping flash as a digit. The '13' should be just '3'.
I know that the F head is probably not everyone's forte here on the 3a site, but thought I'd ask here if anyone knew or could suggest places to look.
Gonna go post out to the 3B forum and maybe a CJ5 forum to see if they have any ideas.
F Bill - truck engine...that's a little more than I knew before.
Thanks for the input!