51 Chevy Truck Rearend Swap?

[TimS37]

I want to swap out the original 6-lug rearend for a 5-lug rearend. I'm planning to put 15" rims (8" dp.) and am concerned about the width of the new rearend being to wide. I'm also putting a new parallel leaf spring suspension kit on it. Currently, I have a '80 chevy truck posi rear which is very close to the same width as the original rear but the truck has the original ride height. The new rear suspension kit will lower the ride height, so I need a rearend that will allow the wheels to fit into the wheel wells. Does anyone know what year and type of rearend would work for my situation? I've been told 10-bolt chevy rearends but not specific ones. Does anyone know?