Hard drive tops can be a complete PITA to deal with. Some tops are strictly Aluminum or Brass or Stainless Steel or just Steel. Some tops are mostly Aluminum with a Stainless Steel or Steel plate. You can also have a mostly Brass top with Stainless Steel or Steel plate. I grind every top because you never know what you're going to get. I also take a magnet to multiple spots on the top. If the magnet sticks at some places and not others, then you have an Aluminum or Brass top with a Steel plate. You can remove the Steel plate with a plyers and screw driver.

As far as the heat sinks are concerned, my yard takes most of them as extruded. There are some cases where they are considered sheet Aluminum(there is a difference with the heat sink fins). One thing you should do is take a grinder to them. Some heat sinks that look like they are all Aluminum are actually coated copper. In your picture, all look like Extruded Aluminum except the bottom right one(and maybe the 6 in the middle, they might be cast but my yard would probably take as extruded). Grind the edges and the fins on the one at the lower right. If everything is copper, then throw it in with number 1 copper. If just some of it is copper and the rest Alum, throw it in with Copper/Alum rads. If it appears to be all Aluminum, the I would throw it in with sheet. Reason being because the fins in the middle look like they are sheet.