I would move fast, or you'll still be waiting for your upper in June.
I have a Black Rain lower, I would highly recommend matching yours up to one of their upper receivers. Actually, their 3R barrels are really accurate, here is a pic of a build I did with one of there lowers, upper, and barrel. The rail is a Daniel Defense Omega rail; I'm not that pleased with the rail.
Hk USP 45 Expert, USP 40, USP 9, SIG P226, S&W M&P9, Hk 4, Makarov, Desert Eagle 40, Beretta FS92 Centurion, Kimber TLEII 1911A1, Glock 22, SIG P225, 1943 Rem Rand 1911A1, S&W mod 64, Walther PPQ, SIG P229, Browning BDA 45 (SIG P220), Hk45, SIG P230