While I would happily buy Chinese made cyl heads, I would buy them bare. I would not trust their springs...or valves. These two components are under tremendous stress & it is most important to use known, quality parts. If they fail, they can do a LOT of damage.
Agree with Ken, 120 lb on the seat, 300 open, less than 0.525" lift should be ok. 145 lb on the seat is getting into roller cam territory.