Mitchell is a 26% or 36% overdrive depending on what you choose,a 3.54 is about a 10% increase in road speed over a stock 3.78..so basically if a stock A is happy at fifty mph,yours does 60 with the 3.54 and say you buy the 26% OD you would top out at close to 80 mph..heres the neat thing about the Mitchell,you can 'split' gears so instead of three you now have six..so the additional torque load of the 36% or (46% if you choose)on the engine is moderated by six gear combinations..you might shift more,but keep in mind the mitchell is syncromesh,you can actually never have to shift the flat gears against load again..I was on the fence till I looked at it..
http://mitchelloverdrivemfg.com/
Not anymore..