yes they all inter change with stock axles
IMO.3.55 is the best all around gear for street duty and towing with a car
3.23 are a little better for gas milage
2.?? are for highway cruz and no towing for mpgs
3.91s are great out the hole,but 3500rpms at 60mph and no mpgs over 70mph
results will vary with gear and weight with highway speeds and towing
what engine and tranny combo???thats gotta be figured in as well as tire size for rpm/mph/mpg results
80 mph should not be a problem with any gear,the weight,distance,rpm,mph,mpgs,milage traveled will though