If you want the best build quality and best light pattern, you definitely want new GM/ACDelco housings. They are expensive though.
The Spyders mentioned earlier in this thread and Anzo 111004s are an acceptable (in my uneducated opinion) cheaper alternative if you're OK with the clear lens look. The Anzos are a very similar design to the Spyders, but with plastic lenses.
https://www.amazon.com/USA-111004-Chevrolet-Headlight-Assembly/dp/B0015PPZMC
The Spyders mentioned earlier in this thread and Anzo 111004s are an acceptable (in my uneducated opinion) cheaper alternative if you're OK with the clear lens look. The Anzos are a very similar design to the Spyders, but with plastic lenses.
https://www.amazon.com/USA-111004-Chevrolet-Headlight-Assembly/dp/B0015PPZMC