I have a 2006 F-150XLT SCAB Longbed(8')...this is the 4dr with 1/2drs in rear and than since it has the longbed and 4x4 5.4L V8, it has 4.10 gears in the rear. The wheels are 7lug! Currently I have stock wheels 17" with 245/70R17 tires. I also have a tall cap on it as well.

I don't have the $$ for a lift kit, nor do I think a lift on this long (~21') of a truck would look the greatest. I've heard of putting block spacers though into the front shocks as a sudo-type lift...the more I research this, it is considered a leveling kit though right?
The reason I ask about this is because I need new tires and hate the stock aluminum rims. I want to dress up my truck with some good black/stainless (chrome or polished look, not necessarily chrome) mixed rims. I wanted to increase the rims to 18" or 20" probably and put some more aggressive tires on them as well going up to 33" or 35" tires. I want the truck to not be obnoxiously annoying on the road but at the same have some good tires to put it's power to the ground when offroad. I was asking about the "spacers" to maybe lift it a little as well as increase clearance for bigger wheels/tires. I wouldn't mind the tires sticking slightly out of the wheel wells (width) but my primary concern is that I want to go bigger without it rubbing.
I also want to go with the wheel/tire ratio that would give me a good amount of side rubber (near stock). In other words if I can only fit 33s even with spacers/leveling kit and 20" rims with these would make them be nearly low profile wheels i don't want that either.

I'm not sure how I can figure out how big I can go with wheels/tires without clearance issues, even when turning.
Can anyone recommend good spacers/leveling kits, sizes and brands that aren't too $$?
Also, please recommend how large of wheels/tires you think I can go with (height and width please)to go along with wtv recommendation on spacers is or if I shouldn't use spacers and what wheels?? Please throw in pictures and brand/type recommendations if you can.
I'd like to do 18" or 20" wheels with 35"s if I can get the clearance, and if the $$ isn't too much...
Thanks!