I would be interested in seeing a picture of the Tractor as it must be a monster, or if not, you must have some low bridges in your neighborhood!!
I used to drive a '62 GMC 6500 that was probably about 6 Inches taller at the bed than your truck will be and I would carry full units of lumber, 3 high. We would be bordering 13 Ft 6 Inches at times, but I never hit anything, luckily anyway.
I actually would not recommend lowering your truck any except for maybe some Low Profile Tires if necessary.
Also at 10K Lbs for your Tractor and the weight of a Sliding Steel Bed, you will be real close, if not over your GVW.
Have you considered towing it behind on a trailer instead?
Nice looking truck there, by the way.
Bill
