I'd go with what ever motor you can find, that's in good shape. In stock form either of these motor will flat out blow your tbi away. You will be happy with either one. If you go with a 6.0, I like the lq9 better then the lq4. It has higher compression for a bit more power. If you think you will ever go forced induction, then go with the lq4. I have installed a few of these motors, and loved them all.