@eholden Welcome to our collective backyard! That's a fine looking Explorer, if I'm one to pass judgment.
The factory running boards do reduce clearance significantly; if you're planning on beating around on this one, I'd do some searching with the bar on the top right corner to see what others have done for sliders or nerf bars.
Is this for real performance, or just for looks? Your Explorer looks really clean as it is, and the body appears to be in near-perfect condition. If you're planning on anything beyond gravel and dirt, before you even worry about sliders and the big stuff, I'd recommend some smaller wheels and taller tires. More sidewall means you can air down to get more traction and flex; if you tried to air down the low-profile tires you've got now, you'd probably bash up the wheels pretty good before you got much of a benefit from it.
Looks like you've got a good tread pattern, but trust me, tread pattern means nothing if you run full pressure. If you just want an aggressive-looking street cruiser, I'd keep it how it is, or simply remove the running boards. But, it's your toy, and you can play with it how you like!
