I have the '86 factory service manual, it comes in 3 volumes and it has a lot of useful info. It covers all the F series F150-350, so much more than just our trucks. The most useful part of the service manual in regards to our trucks is the diesel engine supplement that was mentioned. In my manual, this is a subsection. There are pdfs for the 6.9l diesel supplement out there on thedieselfiles.com, but I don't think they have a copy of the 7.3l one. The thing to realize about the service manual is that anything shared among the F series such as non-diesel specific powertrain components, isn't going to be in the diesel supplement. The diesel engine supplement is almost entirely related to the engine itself. If you need diagnose something such as fuel system problems with the tanks or FSV, that section isn't located in the diesel supplement part of the manual. Depending on your budget and what you need, it might be worth it just to buy the entire manual from Helms.