AR15/M16 Rifle Parts & Accessories, Flat Top Upper, Rear Sight - SARCO, Inc.
pretty good price on stripped a2 uppers.
the $40 a2 type have a sandblasted finish. the $45 a2s have the GI finish and probably a little wear. but for a retro build i don't see how you can go very wrong on um.
be aware that these probably don't have the m4 ramps. if you have a m4 barrel extension you'll have to blend them in.
my new a2 LAR upper i blended to the DPMS barrel, not really much to the blending part.
though i have been told that mall-ninjas drop dead at the mear "thought" of a tiny-teeny bit of grinding, filing or fitting!--LOL
this is a sarco deal. so far i have had no problems with their e-sarco orders --YMMV though.
mine came out to $50.95 shipped. so there S&S ain't too bad if you don't dog-pile your order with a bunch of extra stuff.