I was looking at purchasing a set of Crane push rods. I'll be running a XE268 Comp cam with 1.6 rocker arms. Cranes push rods (cheap set) are 7.818 long, what kind of problems will I have since they are .018 longer than factory push rods?

 

.018 is not enough to make a problem.

If you're using guideplates, you need to make sure that "cheap set" of pushrods is hardened steel. Otherwise they'll rub away little flakes of metal into your engine at the least, and bend/break at the most.