As an FJ owner up until 6 hours ago, I can say that I preferred the 16" TRD wheels over the typical stock 17" wheels. The 17's may be better on the 4Runner, but I drove a lot of FJ's before picking mine, and I thought the 16" TRD's looked the best, and it was the best off-road and it felt very good on the road. I am not a super offroader, but I know the 16" wheels provided an advantage offroad (more sidewall I guess, since the vehicle was the same height, but the tires had more rubber to make up the difference).
You can get the TRD wheels for a pretty good price directly through some dealers. Then put a better tire on. The BF Goodrich that came on my Trail Teams were an incredible tire. I don't know how they did it, but that thing ran quiet on the road, but was the best off-roading tire I've used (that is still quiet on the freeway). It is a good compromise if most of your driving is freeway, and they were also quite good in the snow.
FJ wheels are pretty easy to find as the previous poster suggested. Tons of the members of the FJ forums pull their wheels and sell them immediately upon buying the vehicle because they hate them and they are putting lifts on and such.
I wouldn't hesitate for a second if I were to switch the wheels on my upcoming 4Runner to put the same wheel and tire combo I had for the last two years on my FJ Trail Teams. They are excellent. I know many of the FJ club members and members here will disagree with me and talk about the super offroad tires like Revos and some guys were really into the Yoko MT's and such, but for those of us who still use them as a daily driver then it is about compromises that still give you the best you can get in multiple situations and I felt like my Trail Teams was set up perfectly for off and on road and my family never complained about ride quality or noise like they used to in my Trooper (AKA the Sherman Tank) or the Pathfinder (AKA the Wobble Machine).
Just another option to think about and no.... I am not even sure if the 16's will work. But I'd be interested to hear if others tried them and if they had a good or bad experience. I would really like to set my 4Runner up like my FJ was. I loved that thing. It just didn't have the best backseat for 2 little kids and my payment was just too high for this stage of my life (the little surprise came along and all of a sudden daycare cost $1000 a month!).
