I;m running a C-4 Gear vendor combo, & its just to much fun, having 6 forward speeds, shifting from say, 1st to 1st over or 2nd to 2nd over u only drop , maybe 250rpm so your motor is always in its sweet spot.
you can put it in manual & shift all 6 gears or switch to Auto & the trans goes thro 1,2,3 & into OD automaticly.
I;ve never done the 1/4 mile since installing but, i have done Mosport, a 2.5 mile roundy world class track, with the C-4 GV unit we knocked 7 seconds off our lap times!
It is a bit pricey, but rebuild a 4R, buy the baumman controller & i think your getting close to 2K ,eh
All that said, shifting can be, how do i say, a bit clunky if your not at the right RPM, so sometimes it is like shifting a truck, my only complaint
I do plan on switching it out tho, & going with Fords latest OD & an aftermarket controller, just for a change