SLP makes mustang parts now? oh jesus...
ive never owned a stang before but id say get a 4.10 gear then drag radials (youre going to lose what little traction you had when you go to a 4.10

) then get a good flowing exhaust and punch out the cat while youre down there. then move onto a cai and long tubes and an h-pipe. dont get shorty headers, spend the extra dollar and get long tubes.