Since its all coming out anyways, I would recommend the 4l80e swap. GM rated the 4l60e at 350ft-lbs and the 4l65e (a "beefed up" 4l60e) at 385ft-lbs in trucks, 400ft-lbs for cars. Even built, they really aren't worth it and don't hold up to big power in heavy trucks. A stock 4l80 can handle...