Regarding the '03 vs. ')3A3 question, I couldn't decide either......... so I did the only honorable thing. I bought one of each. I have a 1918 1903 rifle and a 1945 1903A3.
The '03 is much more carefully made and finished than the '03A3. It has milled parts vs. stamped parts. Its sight is adjustable up to about 2850 yards vs the '02A3 roughly 1000 yards (I think -- someone will correct me. I don't have the rifle with me now). The '03 sight actually has 3 notches and two apertures that you can use. It is a thing of beauty. The barrels on '03's are 4 groove barrels whereas most of the '03A3 barrels were made as 2-grove barrels as a wartime expedient. The aperture sight on the '03A3 is not as good as that on a Garand, nor does it have the range of adjustment that the '03 has, elevation OR windage.
Functionally and practically, the two are the same rifle. If I could only have (shudder) one, it would be a Springfield-produced 1903. After all, we call it the "Springfield Rifle," don't we? Fortunately, I was able to get both, and I am happy with them. $400 is a very good price for a rifle that is pretty much ready for issue to front-line troops. There is plenty of grease, cosmoline, etc., on the pieces -- more than what I found on my Garands, but that just means that they are well-preserved.
Clemson