I can help you with the first 4 digits F353. "F" = COE, "35"= 350 series 2 ton,"3" = 161"in. wheelbase. Your next set of numbers don't seem right 8 S1170D. F353 would usually be followed by "24", which would be the engine cubic inch, of the 350 series trucks. Then a four digit serial number. Example "F352 24 1170". Also "FF"= 1947-'51. "F"= 1952-'55 1st series.

Spanky Hardy
Collector Of Fine Old G.M. COE Trucks & Antique Holmes Wreckers

1948 Chevrolet 5700 COE Holmes HD W35 Wrecker
In the Stovebolt Gallery
More pictures on Photobucket

1950 GMC 250 1-Ton
In the Stovebolt Gallery