Need help determining which front spacer lift to use, help!

I installed Supersprings (add-a-leaf thing) onto the rear leaf-pack of my 2005 Toyota Tacoma. It raised the rear of my truck more than expected, so now I need to level out the front. I have a couple questions.

#1: My mechanical knowledge is definately inferior, so I am asking, how many inches can I lift the front with just an aluminum spacer, and NOT have to worry about replacing the other front end "stuff" whatever that might be (diff drops, control arms, shocks etc...) Am I safe to assume I can use up to a 3" spacer without needing to install or adjust anything else? If not, how about a 2.5" or 2" spacer?

#2: I was a fool, and I did not take measurements before installing the Supersprings, so I don't know how much higher the rear end sits than before. How do I determine how many inches of lift I need up front to level it out? I have seen 1", 1.5", 2", 2.5" and 3" aluminum spacers for sale on line. How do I determine which one to select? I rarely have a load in the back of my truck. In case you are wondering why I would install the supersprings in the first place if I rarely carry a load, the answer is that the STOCK rear suspension would bottom out very easily whenever I go over a big bumps. There is a TSB for this, my truck is not in warranty anymore, so I turned to the supersprings for a quick fix and it indeed solved the problem. Now I just need to level it. Anyone who can help me out I would GREATLY appreciate it. Thanks!!!!