"...and my EMT is steel, so I figured that's the right choice"
No, aluminum will work just fine, in most cases.
Greater impact resistance is one of the reasons to insist on steel (actually malleable iron). But if that is the case, why would you use set screw connections or even EMT to begin with ?
You need a 3/4 type C conduit body. You want the threadless setscrew type and "steel". Unless you give on one of the wants, you may not find it.
Or, buy a threaded malleable iron one, and use fittings to adapt to a threadless setscrew EMT connection.