You have been around more of it then. I didn't understand years ago about reading the sparks better on cast grinding test and looking at the grain to identify it better but it's good to know & learn. Have read up some on casting but never set up a furnace yet and knew they had additives to change cast quality and other stuff to add makes the impurities settle out for a better quality cast. One other main place that still casts new reproduction parts today for antique tractors and others things is Rosewood Machine in Rosewood, Ohio. Before oil bust of 1980s you could go into many specialty casting shops here in Texas back then for repairs on cast they had huge ovens would hold more than one V12 Waukesha block at a time. They made it look easy repairing heads, blocks, manifolds and other things look new again but we paid for it back then too. Now Rosewood has new manifolds and other parts for about same price or less than we paid to have those same parts fixed 20 years ago lol. Reproduction cast parts I get from another place are made in Taiwan or who knows and I was skeptical on their trans gears made for a JD tractor at a fraction of jacked up JD price but this guy has had them in his tractor he works now for 10 years or more no problems the quality actually looked good on them when they got here. Now most of the scrap metal places don't sort cast like they use to or doesn't matter on their selling end. One scrap place here the old guy knew by looking at engine heads, blocks, cranks we dropped off and he wanted them sorted as unloading because cast was better quality he could get more for it sorting it.
http://www.rosewoodmachine.com/Merchant2/merchant.mvc