Have to disagree with the fuel mileage. Without a turbo, and if it's a 3 speed C-6, it will only get 11 mpg's. If it's the 4 speed manual, then your looking at a little better mpg's at 15-16.
87 was the transition year from the 6.9-7.3 idi motor so it could have either in it.
Look at the body close when you take a look at it. When I scrapped out my old 87 6.9, I found out that even though the rocker panels and wheel wells were in great shape, the body mounts were shot. So check the body mounts under the cab and the two up front around the radiator area.
All in all it would be a good starter truck as my old 87 was for me. I got 3 good years out of it and was in the same situation where it only got used when needed. I maybe only put 4k miles on it a year.