Factory Service Manuals
 

I found this ad searching for '91 F700 manuals and purchased 3 for $75 plus shipping. By far the cheapest I have found and this guy is straight up, really helpful, honest. He has all kinds of manuals available, if you can't find what you're looking for just send him an email and he'll let you know if he has it or not.

FORD CAR TRUCK FACTORY MANUAL