I usually post on the 73-87 side but I have collected copies of most of the 67-72 light truck service literature.
PDF scans of 1967-1972 GMC and Chevrolet Light 10-30, Medium 40-60, and Heavy 70-90 Truck Service Manuals from my library.
The links are to the PDF files on MediaFire.
I personally like paper manuals that I can hold in my hands. These PDF files are a good compromise till you can buy a hardcopy. I made them searchable allowing me to find the pages I'm looking for and slip in bookmarks so I can find them again in the shop.
The paper manuals aren't expensive and are well worth buying used when they come up.
I will eventually scan and link all the manuals on this list. If it's not listed I don't own it.
Wiring manuals cover all GMC light through heavy models in the year listed.
My scanner only handles 12"x32" pages. The longer fold-out pages in the 68-72 wiring manuals have been scanned from both ends and stitched to the full original length.
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1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8
RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.