Are 3.55 gears a good choice?
I have 904 automatic, 3.55 Suregrip 489 - 8 ¾” rear end under my Dart with 205/70x 14 tires. 60 mph is a busy 3000 rpm out on the road. It drives me nuts after a while even with new quieter mufflers. Gas mileage is around 17.
The problem I have with this engine is the cam likes 3000 to 6000 rpm, and is a turd below 3000 rpm, she was a former drag queen. So driving around town, and on the open road is just under where the old slant likes to pull hard. Get the rpm up into 4000 range and this car comes alive, along with the secondary’s killing fuel mileage.
With 3.55 gears one needs a taller tire, and a low rpm torque cam to be a nice quiet street car. The other thing is, back forty years ago, no one gave 3000 rpm on the road a second thought, but today’s cars are geared to run at 60 mph just under 2000 rpm. We have grown accustom to our engines running just over a high idle for hours on end.