What would be the best year rear end to change my 57 truck rear end out to. The stock Rear end is to low for the 350 auto trans I am running now  

I would recommend getting one from a ‘73-‘87 Chevy. You will get the same lug pattern and leave spring perches. I'm not too sure about the width compared to your stocker.

You can also look into having the gears changed in your stock rearend. It most likely has a 4-series (4.10 or 4.56) gear in it now so look into 3-series (3.08 3.73) conversion gears that will fit on a 4 series carrier.