I would think the 03-04 2uz out of a GX470 would be the bees knees. You lose the VVT-I which is a bummer ( should be easier wiring though ) but you still get the 5 spd auto which should help things out. I'm not sure what the weight difference is between a stocker GX and an 80. I know the wife's GX feels like a missile compared to either of my 80's.
The heads swap easily, so you can get your VVT-i back.