What is a sas or a sloped body lift and are they safe to do
SAS is solid axle swap. $$$, knowledge and time.
Sloped body lift is a body lift in which the lift pucks decrease in size toward the back, each one consecutively smaller than the previous ending with no puck or a small puck for the rearmost puck. Gives about 3" in the front decreasing down to 0" in the rear.
A spring over is going to give you 5"-6" of lift depending on your leaf springs. Do you currently have a monoleaf (a single rear leaf spring)? You would want to change that to a 4 door Explorer set of springs.
To get similar lift out of the front on your 4x4, you'll need to do one of the following in order of increasing price and badass-ness.
1.) Sloped body lift and 2" torsion twist
2.) 4" Suspension lift (Superlift)
3.) Long travel kit (Dixon Brothers, maybe some others, I don't keep up w/ desert trucks)
4.) Solid front axle
What you can/will do is going to depend on your intended use, budget, and timeframe. You'll need deep pockets for #3 and #4. You'll also need considerable fabrication skill for #4 unless you really want to pay a lot to a shop.