The R 180 worked great as a road race/autocross unit.But, would snap halfshafts during a hard drag launch and this was with Hoosier dirt track tires.With slicks and high HP the R200 or R230 is the only was to go if the IRS is what you want to stick with.I ended up selling the R180 with 4.11`s and buying a NISMO LSD and putting it in a R200 with 3.70`s.