Question re: older vehicle maintenance...

1) 1999 Ford Ranger, 6 cyl, auto, 230,000 miles

2) 2003 Ford E350, 7.3 diesel, 260,000 miles

Both have been mechanically very well maintained, despite their looks.

What would be the best maintenance/repair manuals for this age of vehicles? Chilton? Something else?

You know…electrical diagrams, part numbers, etc, procedures/instructions for removing/replacing that hard to reach doohickey that you can’t even see up under that other stuff that you don’t really want to remove if you don’t have to.

And where would I purchase such a manual?

Thank you for any suggestions.