best cruising gear ratio 440 Duster

It's a 440! They have more torque at stall on the primaries,than most teeners at their best. So lose performance compared to what? lol.
Compared to the same 440 with 3.55s still probably not, cuz the tires give up either way. With 3.55s you just have to shift sooner,lol.
If you own "em, stick 'em in there.

336ft, eh! That's pretty good.