As post 2 said it is just a serial number on the frame. It should be on the top of the left frame rail near the steering box. It should be star, 18-, a 6 digit number followed by a star. Frequently the stamping is faint. The same number without the 18- prefix is probably 2 more places on top of the left frame rail under the body. See also http://www.vanpeltsales.com/FH_web/flathead_serialnumbers.htm Charlie Stephens
ok i found it. but i have another quick question the serial number is BBI8-xxxxxxx the 3rd prefix would that be the letter I or is it a 1? because it looks like I
Go to http://www.vanpeltsales.com/FH_web/flathead_serialnumbers.htm and you will see that Ford used I for 1 (the letter I for the number 1). I think the BB means you have a 4 speed transmission, probably in a large truck not on the passenger car chassis. Charlie Stephens