Any reputable company will be glad to share who they are partnered with in a venture like this. If they're crooked, then they won't share the information, simply because of fear that someone will attempt to buy direct. The thing is, though, that if there is a good relationship, the manufacturer won't do business with anyone except the company they're in business with. Much the reason it's a partnership. The other reason they wouldn't share is because they know their manufacturer is cut rate. All the machining in the world doesn't cause the casting to be of high quality. If the cast material is bad, then the whole piece is bad. There are exceptions, though, such as paper weights and... ...well, I guess I can't think of any others.
All that being said - If the only choice is a chinese casting, then find an old used one (OEM) or do a gasser transplant - period. If the casting is from Brazil, then you've got a MUCH greater chance of the quality being what it should be. Our experience on chinese castings over several years (on things that are not rocket science) is that they're TRASH.