Those Running 3.73 And a TF w/ LockUp.. What's your highway Driving Like?

2.74 x 3.08 = 8.44
2.74 x 3.27 = 8.96
2.74 x 3.55 = 9.73
2.74 x 3.73 = 10.22

2.54 x 3.08 = 7.82
2.54 x 3.27 = 8.31
2.54 x 3.55 = 9.07
2.54 x 3.73 = 9.14

I realized since you have a lockup 904 you have a lower 1st gear than an earlier non-lockup 904 or 727 (2.74:1 1st vs. 2.54:1). Above shows some quick math for the starting ratio. General consensus is a 3.2x final drive ratio is the ideal compromise gear on muscle-era cars with the taller 1st gear autos but with your lockup 904 your starting ratio is actually a tad deeper than that with 3.08 in the rear end. The lower 1st gear basically makes the starting ratio the same as one step "up" in final drive ratio. With that in mind, I'd go with 3.08 in a heartbeat. That will also match up well with an 8-speed down the road as @DionR pointed out. Not to mention doing ring and pinion changes in an 8.8" isn't as easy as in an 8 3/4" with its dropout center section so picking the right ratio the first time will save a good amount of work later.