I treid 4.30 to 3.73 in my street car, 700 + HP N/A, no differences in at the track performance other than it seem to be in high gear a lot longer with the 3.73.That was with the 8 3/4 that i bent the snout out of three years ago now (It has dana 60 truck housing with 4.10 in it now ) That was with the M/T ET Street Radials 315x60x15 tires at 128.6 MPH with all four sets of gears I would put the 3.55 in it, more pinion tooth contact to the ring gear teeth