I think the major difference is people is comparing a 4 speed vs a 6 speed. With the lower first gear ratio in the 6l80e I think 3.73's would be about as low as id go. Install a converter and keep the 3.42's. Then if you think it needs more then go gears. I think with a 6l80e with 3.42 and a converter it will give you the torque mult. that your looking for.

 

That is if you have a 6l80e. I just saw you have a 4.8 if you have the 4l60e then definatly do 4.10 or 4.30 and a converter