Can't decide what would be my best option for a swap into my 03 1500 The 4bt, the 6.1 hemi or the 6.4 hemi... Any input?

 

4bt will need a different transmission plus doesn't' use electronics so you'd lose your dash, etc, also require custom mounts. 6.1 will bolt in and to your trans, however you won't get full benefit out of it since the 03 PCM is about useless for tuning. A factory 6.4 is a VVT block with MDS, the VVT will need to be locked/disabled, as will the MDS, the engine will physically bolt in and to the trans but again marrying your electronics to it will be the bitch. Closest to a drop in will be the 6.1, but even then there is a ton of **** you'll have to modify and change.