I've done a preliminary search, and it looks like your family is going to be pretty tough. I'm actually fairly sure I've found the right Capooth family, simply because the name is so rare. If it's right (does the name Clarence ring a bell as your great-grandfather?), then I should definitely be able to trace that. The rest of your grandparents are the difficult ones: Herbert Allen is a pretty common name--- if you have any idea where he came from originally, that would help immeasurably.
The DeLong side is also a little tricky, because both of your grandparents look to be relatively young. Do you know if they came from the area of Dexter City originally? If so, did your grandfather possibly have a brother named Wilbur? He would have died in the 1950's. Possible his mother's name was Alma? This family would definitely be worth pursuing, if we can confirm that it's the correct one.
So actually, we're not in bad shape; two of your grandparents are possibly found, the other two might take some work. Let me know if you're interested, and definitely send along anything else you've heard!
All the best,
Travis