if i had to do it over again i would definately get the 4.10's , your heavy beast really needs more gear than the 3.73's, why not some 4.30's ? just kiddin

and about the shift kit, stay away from the B&M, its junk, i had it in mine before i got a rebuild and it sucked a$$ , they guy who rebuilt my tranny made a custom one for cheap and it is way superior to the B&M, go for the Transgo or Baumann like suggested before
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88 Notchback 5.0, 3.73's, pulleys, BBK headers, off-road H-pipe, flowmasters, subframe connectors, 65mm TB, shift kit, March ram air kit, motorsport wires, MSD coil, upper and lower control arms, 155lph fuel pump, cheap 2800 stall, Crane Adj.FPR, best time- 13.99@99.75, not yet tested times after 1.7RR install
