Ordered a gear vendor, help with deciding gears

Have a couple friends running gear vendors. One is a 73 challenger with a 500 inch big block. The other a 73 dart with a 408. ***** run 3.55 gears which when on od makes them around a 2.76 gear. They are both very happy with them. Guy with the challenger has put a ton of miles on his car. Did the power tour with it too.

your friend with the dart is happy with 3:55 gears, not thinking of going 3:73?