No. The 2.66 has much wider spacing. Although they both have a 1:1 4th gear.
Check out the ratios here TREMEC MAGNUM XL T56 6-speed Solution to poor shifting in S197 Mustangs - Modern Driveline
Notice the ratios? If you go with the 2.66 first, it'll be like the MT-82's 2nd gear, and the T-56's 2nd gear will be like the MT-82's 3rd gear.
Not good IMO, unless you're making some crazy horsepower (FI), you'll probably be slower than before. Not good.
The 2.97 looks just right with the 3.73's.
Your MT-82 is a 3.66 first gear. You'll be dropping down a whopping 20% to a 2.97.