Your best bet would be to purchase an aftermarket complete manual, Chilton or Haynes etc. The diagrams I have found on the net are sort of hard to read. Also try Google 67-72 Chevy trucks and you will find a forum with lots of good info.
where can you find a website for free diagram of tail light wiring on a 1994 dodge 1500 truck?
You can find a wiring diagram for a Caterpillar 416 diesel engine at most Caterpillar dealerships. You can also find the wiring diagram at most truck part stores.
In any handbook which shows the wiring diagram for the F350 for that year.
try haynes.com.
Classicarwiring.com (eBay)
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pdftown.com
A person can get a wiring diagram from the cars maintenance manual. They can also ask for a print out of the diagram at an auto part store.
A complete diagram is available at MOTORLIT.COM.
The library
Contact an International dealership
Brothers Truck Parts or LMC