I knew I came to the right place for advice
The 6.9 I'm planning on looking at is an '86. I did hear they were improved. There's an '89 7.3 that a friend of mine test drove and said it runs and drives great. Has 130K miles, which isn't bad. But I'm kinda nervous about the cavitation issue. I'm going to try and buy some test strips, and then go take a look at it I guess. I've wondered how much to REALLY worry about this issue though. I read on a diesel forum somewhere where the concensus seemed to be that it'll happen at around 150k miles if it's been really neglected, and this one is approaching that. I stopped by and looked it over and kicked the tires one day, but no one was around. Maybe I'll go back to take a second look.