Best Gearing for 8 3/4 Behind 1970 Duster 318

Since it ain't cheap to set up new r&p's these days, i would base your choice on if you plan on any future upgrades. I ran a mild engine combo with 3.73 and 27'' tires as a daily driver with a average around town speed of 45/50mph and only several 150mi trips to the beach that were kinda aggravating. That combo puts your rpms just under 1/2 the mph, like 60 = 2800ish. It sounds like that is livable to you, but with that said and no plans for a bigger cam or a racier setup, i'd probably go in the 3.23 range. That would be plenty peppy for what you have now.