Rear gear advice

If the rear is a good deal I say get it. A-Body 8 3/4 rears are hard to find these days. I have 3.55 gears in my Duster & I plan to use 28" tires which will give me 2747 rpm at 65mph. Here's a formula to use. 65(mph) X 3.55(gear) / 84(28" tire diameter X 3) =2747. There's always the 8 1/4 rear as an option.