Ben,
The tracks are fine...solid guide horns were in wide-spread use (and appear simultaneously with hollow guide horns as well) from 1943 onward. They can work for you but you'd be better off accuracy-wise with ATL-27 since those have the chevron-cleat faces.
You're also fine with your choice of barrel and muzzle brake as that style was in use until very late '44 (October-November) when the full circular brake began to appear, so it's quite possible for it to still be around in '45.