Swapping a 1970 3/4 ton rear end

[Lil Chevy Rider]

Right now I have a 1970 Chevy CST 3/4 ton pickup that had a 350 engine and I swapped it to a 1977 350 Monte Carlo engine and auto tranny. Right now I have a heavy duty 8-lug rear end and want to change it to a higher gear 5-lug rear end the easiest possible way that doesn't involve a lot of messing around like if theres one you can just bolt right in. If anybody knows what kind of rear end would go best or what it takes to do a rear end job, any advice or comments would be appreciated.