Mostly cost and known performance. I could pick up the DSM drivetrain, ECU, and harness for about $500-700. I also know what the 4G63 can handle and can find parts very easily. Also, unless another engine and trans will just bolt in place, then I am going to have to fabricate engine/trans mounts anyway. One key piece to this puzzle is that the 4G63 trans will mate up to one of the factory gear ratios in the 8.8 rear end, which there is already a kit out there to bolt into the car. That means that I don't have to deal with cutting the rear pan out and putting something in place that has to hold a rear diff. I know it can be done with anything really, but this is the simplest way that I see. I don't see any hurtles that any other drivetrain will save me. I still have to deal with the rear end, wiring, fuel, axles, engine mount, etc no matter what drivetrain I get.
Andrew-aka The Swap Shop
ZX3 going AWD