It's interesting how everytime a supra thread comes up inquiring about how to mod 2jz gets spouted off really quick. Nothing wrong with the 7m, 1jz, or the 5m for that matter, 2jz is a little over rated imo. Look into the aftermarket for the 5m and compare it to the other motors and make your decision that way.
It's kinda like how everyone with a 240sx pees their pants over a SR20, when the KA motor has just as much potential.
I think the MKII's are pretty neat, not my style, but they can make good power, but Supra's tend to have a heritage of straight line racing. Props for wanting to tackle the corners..