I have a 1958 F100 stepside but I can't find any photos that match mine. It has "Custom Cab" on the doors and it has a full wrap around rear window. Most of the 58's I've seen have the flat rear window and very few have a stepside.
When I got it somebody mentioned it was a 58 1/2.
Also can I use the vin# to verify anything?
any info would be greatly appreciated.  

Get a catalog from LMC. They tell what the vin# stands for in the front of there catalog.  

bbw and custom cab were all options of build level, step sides only hold as much as a wheel barrow, so from a work vehicle point of veiw, style sides were more practicle.