4.71 vs 4.56 gears
 

My 2003 Mach 1 is about to have a fresh rebuilt t56 installed. I have a McLeod clutch, FRPP billet steel flywheel, adjustable clutch cable with aluminum quadrant, and an MGW race shifter. The big question is, do I run 4.56 or 4.71 rear gears for the few years between now and boost? 4.56 would put 1st gear right around where it would be with 3.55 gears in a tr3650, and the rest of the gears would be fairly close to the same ratios as with 4.10 gears in a tr3650. 4.71 gears with the t56 would put 1st gear right around the same spot as 3.73 gears in a tr3650. Obviously, the rest of the gears in the t56 with a 4.71 rear gear ratio would pull a bit harder, and ride slightly higher in the rpm band, than 4.10 gears in the tr3650.
4.71 gears made by US Gear
4.56 gears made by FRPP

I did 4.56s with the t56. My thinking was I drove mainly on the street and often times 1st with 4.10s and the 3650 was useless unless I wanted to burn some tires up.

Re: 4.71 vs 4.56 gears
 

I have 4.56's w/ a T56 in my 03. Quick as can be on the street. Absolutely hate the freeway. Did I say it hates the freeway? Ha! Could not imagine any more gear...