The Rigid Running Boards (option code KH) bolt up to the 2014 SR5's with no modification required.
I bought an SR5 that off the lot last November. It was equipped exactly as I would've ordered it - trim level, color, options - minus the running boards. I figured it would be a piece of cake to order them from Toyota after the fact.
As it turns out, the KH boards are not available through Toyota's accessory catalog. Trying to order a set through a dealership's parts department is a huge headache - they'll get confused and try to sell you the silver-trimmed accessory running boards, or tell you that the boards don't fit an SR5. I was finally able to get a parts guy understand what I wanted, and he was able to pull up a schematic of the running boards showing all the required hardware and part numbers and everything. However, even though the KH boards are a port-installed option, there is no easy way to order them as a kit, especially at anywhere near the $345 MSRP. The only way I found to get the things from Toyota is to order them through the collision catalog (i.e., as replacement parts) but the cost is exorbitant - over $900, IIRC.
I thought about going with sliders, but I thought they might be overkill for me. I really just wanted a step so that my boy could get in and out of the truck more easily. And I liked that the plastic is non-skid, versus the many sliders that are bare metal. And a lot of sliders required welding, and decent ones seem to start in the $500-$600 range. Finally, I like that the KH running boards have a pattern that matches the nonskid area of the rear bumper. It honestly makes no sense to me why Toyota doesn't just list these in their accessory catalog.
I was finally able to pick up a set from a forum member here. I guess his truck came from the dealer with them and he didn't like them, or was going to go with sliders or something. I paid under $300 for them, shipped. So I'd suggest searching the For Sale section here, you might get lucky.