yes you can upgrade the xcellerator from the economy to what ever you want or up the 350hp one.with the BD shift enhancer like i had and the same you plan on getting i still would't run more then 125hp extra,the reson i say that is you'll still have the same torque converter and clutches and you don't want to do a bigger trasnny then you don't want to limp or else you'll almost have to run a built tranny so if you want to do it right buy a stage 2 tranny kit roughly $2k but is well worth it if you are runnin 400rwhp and more and if you plan on going all the way buy the stage 4 with the 1057 converter..
Transmission : Pacific Performance Engineering, Diesel Performance Technolgies
ps i had the ppe hot et 2 on the stock tranny with the enhancer but it didn't take the tranny long for it to be in the blowing apart stage,you can run 200hp to 250hp extra for a awhile but it will do internal damage along the way and cut down on tranny life..