hello bubs- was reading your thread. interesting combination, 63 dart, 170 inch engine, 4spd. od trans and 2.93 diff. that would give you a final ratio in od of 2.15. thats the same deal in the 76 feather duster - think that was the best possible ratio combo for mileage, mine gets 25-32. only differences with yours is the 170 engine which is a little less powerful than the 225 in the feather and i think the feather is a little lighter than your 63. how does it run on the flat in od at lets say 35mph? the feather runs comfortably in od at 30 . plymouth also made a 2.45 diff. always wondered how that would run with the od in a duster. that would give a 1.78 final drive which might be too tall to drive comfortably even with a 318 v8 but that engine would negative the gas mileage. what do you think? regards bob fisher

Bob,
The Dart weighs in at 2700 lbs. pretty light and I have a 225 under the hood. It runs fine at 35 in OD in fact I was wondering at what the lowest speed before shifting into OD would be? I'm in the process of getting tires and I've finally decided to go with the same diameter to match original/stock because I remember how good my gas mileage was with the 13" 185/70/13 now that I have 14'' rims I can put 195/60/14 to match the 23" diameter. It's a daily driver with an occasional hwy trip so economy is my priority.