ohhh...mkay. Btw....the keys you put in are exactly like stock in size and shape, except where the torsion bar slides into the key, it's rotated a few degrees making the torsion bar twist more andin turn pivot the lower control arm, thus creating lift. Same thing cranking the bars does....twist the bar to provide lift.
The one good thing I have to say about keys....is that they let you use your worn out sagging torsion bars because you can put more twist on them and put it back to a decent height because of all that new adjustability because of the rotation of that bar.
Lifting a truck and wanting good mileage is dumb. You shouldn't really care other than trying to get the best out of what you've got. You are VERY lucky seeing the numbers that your seeing...I NEVER saw 19 when I was stock on stock tires and stock gears. I now am seeing about 18 on freeway runs on average, and about 16.5ish with mixed on 8" of lift and 35's with 4.88's. Do you plan on running 30's while being lifted? Remember...you go up, go wide....aka wider wheels with lower backspace and wider tires.
You can run those keys ya...just dont think that you should max 'em out or get anywhere near. Right now with those bolts in as far as they are, you're about at the same equivilent to stock keys being maxed. Lets keep it that way for wear and tear reasons. The superlift requires dropping the bars and keys anyway...so either keep runnin' em or throw the stockers back in.
It's up to you what you wanna do really....I'm not gonna tell you what to do. In my opinion, I like the $200 option compared to the $1500 option with the superlift. Of course...I'm a little biased...I've got a superlift ANd bodylift and on 35's.