I recommend that you build your car and drive it for awhile before deciding to change out the 2.73 gears.

I picked up a used axle with 2.73 gears and fully expected to have to rebuild it which I would have done with 3.55 gears. But once I opened up the rear the gears were in great shape so I just replaced the axle bearings, seals and installed the 5 lug axles.

My Speedstar is not quite finished but I do have about 30 miles on it. Even with 305/35-20 tires on the back the 5.7 Hemi will effortlessly break the tires loose in 1st and 2nd, it will also break the tires loose in 3rd if I try. At this point I can't see any reason I would want to change from the 2.73s.