RE: Fuse Box Diagram for a 1989 Dodge Ram b350
Are you looking for specific information, or just general info?
If you have a Haynes manual you may be able to use the following to figure out what you need. The Haynes manual does something to save space and repeated information though it can be confusing to look at. The '79 - '84 schematic is almost every wire (though I've seen some variation in color codes). The pages for '85 - '87 list the changes from the 79-84 for specific sub systems. The '88 to '91 pages list the changes to the previous two sections that are specific to that series, etc.
The only other options would be to try and find a user man on ebay or in the glove box of one in a yard, or start pulling fuses and see what stopes working. This is easier on the 88-91 series because at that point the switch was made to ATM blade fuses from AGC glass fuses.