Will, The real question seems to be whether you should turn this dilema, into an opportunity to justify replacing the 6 with an 8. Unfortunately, you are the only one that can answer that question. The way I see it, you need to decide what you really want to do with your truck. If you want a highway cruiser that can easily handle 70 to 80 mph speeds go with a V8. If you want something to just have fun with, whether for work or play, look for a good used 6. An inline 6 can handle highway speeds OK, but not quite as well as a V8 will. It also depends on how much you want to spend.
Obviously, a good used 6 will be much easier and less costly than switching to a V8. I think the inline 6's have more character, but that is just my opinion. You can buy far more trucks with V8's than you can with straight 6's. It all depends on what you really want.
Good luck
John