Good choice, I've been running the Tera 3" springs for about 1.5 years now. Very soft highway ride, but not floppy. The 3" springs have a lower spring rate than the Tera 4" springs (stiffer). The 3" springs would be ample to clear 33s. At 4" of lift, you have to go the extra mile to get a good highway ride. Definitely go with a slip yoke eliminator kit, CV driveshaft, all new adjustable control arms, and adjustable trac arms if you are looking at that amount of lift.
BTW- if you get disconnect-able front sway bar ends, the Tera kit is pretty nice- even comes with brake line extension brackets.
Just don't cheap out and skip the SYE kit and CV driveshaft. You'll be kicking yourself in the ass when your shifters are all screwy, you're staring at the transfer case drop, and you're cooking driveshaft u-joints.
Also, do the rear end driveline angles the right way. Spend the extra $70 on rear shock relocators and the Rubicon Express 1602 angled trac arm bracket. When you rotate when pinion up, the rear shocks will contact the spring buckets and your rear trac arm will get very close to the gas tank.
I'm not just pimping my setup here, this is what I have found works best for a short arm TJ lift. I also believe that any TJ lift over 3.5" is better suited to the long arm design (or the Currie J-arm design)- you can only put so much angle on the short arms before the suspension just isn't working for you anymore and the bumps on the highway are shooting right up into your steering wheel.
