missing Vehicle Certification Label - '81 Chev Silverado 4x4 1/2 ton pickup

[Frankenstien]

Hey all ... I just landed here and am hopeful an expert (or owner of the exact same pickmeup truck as me) can help me out with the info I need from this missing label ...

my truck has the 8' fleetside box (131 IN wheelbase), is Model # CK10903 and has VIN # 2GCEK14L9B1 148522 (Note: the Truck Camper Loading Information & Service Parts Identification labels in the glovebox are intact and I have them recorded as .jpg photos)

So far, I've figured out that in 1981, in Canada, GM was putting this label on the upper, rear, inner surface of the driver's door (seems strange to me that an important label would get applied to an easily removable part - oh well). Anyways, my label was no more than a residual glue spot when I bought this truck in APR04.

I've exhausted my attempts to get GM in Oshawa, Ontario (where the truck was built) to cough up the label info - they've referred me to an arm of GM called Vintage - who, in turn, have taken $26.75 off me to provide a letter that states: GAWR Front 3520 Lbs., GAWR Rear 3520 Lbs., GVWR 6100 Lbs., production date of January 15, 1981 (Service Parts Identification label says JAN 09 81) and "Original tire size was a P 235/75 R 15" (this latter portion I don't trust at all, as I have what appear to be 'BW' '15 x 8 JJ' wheels - Service Parts Identification label says 'PA6' (supposedly 'Wheels, Styled') - that, so far as I know, are the original wheels, and, all the P or LT 235/75 R 15 tires I've looked at specifiy a rim width of 6.5", not 8").

The wheel size info and recommended tire inflation pressures appeared on the original Vehicle Certification Label as well, however, Vintage does not / cannot supply that info. The guy I talked to at Vintage (George) mentioned something about deriving the information from 'calculations' - hence, a possible reason for inaccuracies on their part.

If anyone can help me nail down the tire / wheel / inflation info, I'd sure appreciate it.