Welcome to the group and good find there. Correct there are no Marti Reports for 1966 broncos, but also correct they can make a new warranty plate.
The info on your plate is
U13- roadster
F- 170 6CYL
L- Michigan plant
738002 -August 1965 build
092- 92" wheelbase
M- Wimbledon White
U130- standard 4300lb gvw
796- silver front buckets, no top/doors
C- manual transmission
03- small bearing 9" 4.11 open gears
42- Fargo sales area
I do have 738003 on my list, it's Arcadian blue and in Montana. Yours is the 95th earliest known u13 to still survive on my list, production for all the u13, u14, u15 began with 732001 so there are quite a few broncos built ahead of you.