Brownells 20" complete upper (BRN16A2), these are $799.99 from Brownells website

>All new production, no surplus parts
>M16A2 Upper Receiver
>A2 USGI Rear Sight Assembly
>20" 5.56x45mm NATO barrel with 1-7 twist & chrome bore and chamber
>Mil-spec bolt carrier group with phosphate exterior and chrome interior

KE Arms complete monolithic polymer lower.
Battlearms Development enhanced trigger

If the ad is up the rifle is available
I am near the Chandler Airport

https://www.brownells.com/gun-parts/rifle-parts/rifle-receivers-parts/brn16a2-5.56-20-complete-upper-receiver/

https://www.kearms.com/kp-15-polymer-receiver-milspec.aspx