Have you verified with the dealer whether or not the factory shocks for the 2013 are different than for the 2012 trucks? Often the guides are not updated for newer vehicles so they do not show a part number though one for the prior year will actually work.
Factory shocks on most of my trucks have worked well until they wore out and they did not last as long as the replacement shocks. If your truck has less than 30k miles on it the factory shocks should be OK.
The rear shocks are doing 80% of the dampening anyway when a heavy load, like a camper, is in the bed.
I have Rancho 9000 shocks on my truck but when it comes time to replace them it will be with Bilstein 5100's. Not at all impressed with the Rancho 9000 shocks which are no better than the factory ones they replaced.
