Tronman ... Forgive me if I am not quick on the uptake here -- Is the problem that the studs are too big in diameter, they are the wrong hand thread, or all of the above?
Perhaps I'm stating the obvious here and that this is something you already know... But you do know that your truck (if it was anything like my '65 GMC 4400) probably has right hand threaded studs on one side and left hand threaded studs on the other? Did you specify?
If you don't know or aren't aware, the studs will be marked with a "L" on the end if they are left hand threaded.
As for the actual stud size, I don't recall off hand what the correct size is for that truck. There *is* a fair amount of variance among the truck sizes and you need to be specific when you order them.

Again, apologies if you already know this and *did* specify ...

John