As I said in your other thread, I'd sell the 17's and keep those 16's. If not, sell them to me!
Anyway, there are no mods that you can do that will prolong the life of your engine. Even if it's supercharged, it can last quite a while. My old 98 4Runner was supercharged and still ran like a top at 140k. You just need to keep up on PM (preventative maintenance) and keep an eye on things, and it should last you quite a while.
And remember, my 4Runner required premium fuel for the supercharger (the one downside of owning the S/C), so be sure to put that in. I still got great gas mileage at 20mpg on stock tires.