Just to clarify; 2.97 is the WIDE ratio. 2.66 is the close ratio.
*to put this in historical perspective; the 2.52 wide ratio M20; and the 2.64 & 2.43 1st gear T10s are all closer ratio compared to todays 'close ratio' gearboxes*
Id say you're on the right track with your build, given the parameters. Make sure if you get an aluminum driveshaft, A. its spin balanced for the RPMs you're planning on, and B. the tube size and wall thickness are sized properly for your application. You may want to consider a bolt in driveshaft loop as a measure of safety and perhaps a set of 1350-series U-joints
Disclaimer: The following comments aren't meant as a reflection of your build, but rather to point out some areas that other builders may not know they need to take into consideration
You're kind of in a bit of a compromise. In reality; you could put 3.08s in the rear and not even use the OD at all, with that 2.97 1st gear (9.14:1 Starting Line Ratio). Being a carbed car, we need to remember that we can't drop the RPMs too low at cruise, as driveability and mileage will suffer. But, the flip side is: you have a TON of first gear and a stump puller of a motor.
Gorgeous 57 Chevy; and Im sure you're going to enjoy the hell out of it.