I'm pretty sure the shifting is the same if you have it floored for overdrive on and off, I also highly doubt you'll need 4th gear. In autocross it helps to turn off overdrive, that way you don't have to worry about it trying to use 4th. I don't think it would be that good to leave it in 1st the whole time, I always got too much wheels spin out of corners when it dropped to 1st. So, for drag it doesn't matter, Auto-X turn it off.
ATX Faction #16
Duratec Team #60