You should have chatted to me about it last weekend. I plan on jumping to STF from H-Stock.
For start, just worry about upgrading the suspension, and finding the right combination of wheel/tire. If you have the winter package (like me), then disabling the traction control should be high on the priority list as well.
H&R race springs and Koni's should be a good start. I'm looking around to see what coilover set I want. A rear swaybar is a must, if you haven't already. I was planning on the H&R rear bar to start, and if I feel it's not enough, I will consider the Steeda bar.
For wheels and tires, I am going to run a set of 16x7.5 Kosei K1's that I have (there's another set currently for sale on FJ that I would like to buy as a spare set, but you should maybe try to pick them up if you can). Toyo just made R1R's available in 225/45R16, which is what I plan on running for dry days. It's slightly shorter than the stock diameter which will help with the ridiculous SVT gearing. These would work well in the wet as well, but 225/50R16 Continental DW's should be better.
After watching Andy race his 2 the last couple weeks, I am convinced that the SVT can keep up with him, but it's going to take everything we can throw at these cars in order to do so.