[Tf175]

Someone (not me ) cut out a section of the bed base for engine access on our '86 . They did a pretty good job of it,  fits snugly and held down with screws . Not sure I would have cut it out , but it gives good access to the top of the engine . Alternator , compressor , covers over unused drives , etc are all possibilities for leaks . Pdf service and parts  manuals are available online . If you don't already have manuals I recommend getting them to get a better picture of the engine's layout. 
Chris