that was in 5th with the t56 box

the 18" wheels will change the excelleration and the 3.9 diff gets that back for you, with still a very high top end,

yours is being built as a track/road car?

so the 3.6 diff will be a bit high

on my 500 race car last year i was useing a 4.1 diff and that was with 17" still goog for 160 mph and thats more then enough for the track.