new master cylinder or rebuild?

Parts guy is claiming they only came cast iron,yet there is the alum one in this pic?....Probably saying that because it's all he has in stock.

Anyways,the original cast iron master is for power or manual.Part # is the same for either. I have my master completely apart now,except ofr those little brass guys in the brake line holes.Cant see how they come out,was thinking they must have an allen wrench hole deep inside the metering hole,but I cant see in there.