What brand are the levelers? If the front needs to be lifted 8" to level, try using blocks under the jack pads and under the front tires. We use cut sections of 2x12" boards to level on our driveway, which has an incline making it difficult to level.
Here's how it looks...
We first put a couple of short 2x12" boards under the front jacks, then lift the front enough to slide three stacked 2x12"s under the front tires. Let them down so that the tires are sitting on the boards and finish leveling, then chock the back tires. This insures that the jacks don't hyper-extend. We also use those "Lynx Levelers" plastic blocks sometimes, too.