I have the gt-40x crate motor (other mods in sig.) with a C-4 w/ manual valve body. I currently have 3.73's but I plan on going with a lower gear. Either 4.10's or 4.30's. I'm also running 295/50/15 street tires. Since I don't have OD, I was planning on going with a taller tire: BFG 295/65/15...