Flo-tek
Call them up and ask them what city in the USA they are cast in, what city in the USA they are finished in and what name is cast into the heads. If they studder, then chances are they are Asian. That may not be a bad thing for the street, but may not be a good thing if you are going to turn some Revs at the track.
That $75 per head difference between bare castings and complete looks a little too cheap to me to be very good parts.
Some bare heads require valve seat work, resurfacing and guide clearancing plus grinding the new valves, setting spring heights and pressures and assembly cost, whether they are USA or Foreign origin.
And the cost of quality valves, springs, retainers, keepers, seals, shims, etc. add up to more than $150, more like $300.
For $750 for Flow-Me-Tek assembled heads I might want to look around for some Pro Action/ Pro Topline/ RHS/ Comp Cams heads. I have bought new alumninum ones assembled with good parts for less than $100 on this site.
They are cast in New Zealand in an up to date foundry and finished in USA, I believe.