I have a Weaver M73B1, the military marked version of the Weaver 330, but use a Lyman Alaskan for shooting my 03A4 because i t's a superior scope. The Lyman Alaskan was designated M73 and was to be standard on the 03A4, but Lyman couldn't supply the demand, so the Weaver was the second choice.
On Remington 03A3 metal finish, the receiver and barrel were originally parkerized. Virtually all other parts were blued. I've owned new Remington 03A3 parts and they all follow this practice. Parts that are parkerized were all refinished at some point per US Ordnance standard. There's nothing wrong with parkerizing; it just means that parts were refinished.
At some point in 03A3 production there was a switch to a different trigger guard unit with a larger trigger guard bow.
A lot of Springfields show barrels with poor bores as a result of corrosive primed military ammo and/or excessive wear. New GI M1903 replacement barrels are scarce, but can be found for $400 USD if you are lucky. New Rem 03A3 military barrels are more available for a bit less.