Definitely upgrade your Birfs because that will be your weak point right now. I run 38's with 5.29's and locked front and rear with stock birfs right now, I'm upgrading soon but I've been about 5 times and have not had a problem yet. As long as you don't hammer on it with the tires cut too sharp you should be fine for a little while. The birfs will eventually let go with that much rubber on them though. 38's ROCK!
