MJHSC400

Some cars read speed from the diff ring gear-- not sure about the Lex, but others do-- so in that case gearing wouldn't effect the speedo--

You'd just have to find out where the speedo gets it's reading--

As with the shifting-- a shift kit would be in order to take all that shifting and bring it under precise control-- a shift kit can shift faster than any human when done right, and that's the reason you usually see auto's in drag cars-- not all of them, but usually you do with the higher power applications, there's no chance of missing a gear, or slow shifting/driver error...

Plus, a missed gear with 2500 horsepower would probably give you some good whiplash in the old shoulder for a few days.. it would be violent..


As far as higher freeway rpm's-- you could benefit from a piggyback that can control closed loop and lean it out under a normal throttle position for 70-80 mph....

Plus, my sc, which I think is a 3.76 or something, still runs at about 2200 at 80 mph-- so running at 3000 would burn more gas, but I doubt it would run that high, probably more like 2800 or so, and it wouldn't be that big of a deal-- you should get a G20 to drive back and forth to work in anyway-- and just put some s4's in it and surprise the **** out of folks tryin to pass you.... (you can get em for $1000 with a 5 spd-- they're nearly indestructible too)..

But anyway, a shift kit and some closed loop control could keep your mpg close to stock under normal throttle... especially with all your mods---