'87 may be the 6.9 diesel. on a high milage truck this could be a plus as it would less prone to cavitation than the later 7.3. the truck won't win any races but will deliver the goods and get respectable fuel use while doing it. i have a '94 with 275,000 miles that i still drive cross country with no issues. these are good trucks. also, if it has the 5 speed maual that would be plus. parts are also relatively inexpensive as well. check www.oilburners.com
for more info. great forum with some very knowledgeable people on it.