Brent, I have to tell you Josiah had the BEST advice for you.
This is in NO WAY meant to offend anyone posting here. You don't want to rely on some guy two thousand miles away from you with a bent up measuring tape who can't read it properly to give you some numbers.
The bed could be a little off, etc, etc. Getting that HEIGHT hole, yeah, that's cool. "The highest hole is three inches from the fold at the top of the bed side", yeah, ok, start with that. But You REALLY should bolt the whole thing together. Clamp the fenders in place and mark off some holes and drill them.
At the very least, get all the measurements from who ever and DOUBLE CHECK THEM. Before you drill. Mark them on the bed, double check that the fender will be in the right location. Then drill the holes in the bed. Then clamp the fenders in place and mark the fenders thru the holes and then drill the fender holes.
I'll be in Conway this July 8th if you want a hand.
Brian