I tried both the scout scope and a red dot on mine. Much preferred the red dot.
Id also suggest ditching the factory rail and go with something like the Ultimak rail. The factory rail is, or at least was (mine was an early gun) made of steel, and get very hot, very quickly, especially if youre shooting fairly quickly, and stays hot for quite a while. It gets and stays hot enough to burn you too.
It also sits higher than it should.
I had/have a couple of Ultimaks on my AK's, and they work great. Well made, sit low on the gun (I doubt youll get a cowitness with the M1A though), and shed heat quickly and never really get hot.
I always worried about the heat bothering my Aimpoint on the SOCOM.
The Ultimaks are also "mil/Picatinny" spec, the rail on my SOCOM was not, although Springfield swore it was Picatinny. None of my milspec mounts would fit on it, and I suspect it was something like Weaver.