Welcome, nice rifle! An interesting mix of parts. Looks like you need a pin for your front sight base.

The receiver dates to around 1931, the bolt, I think earlier. Early drift slide (horizontal lines touching peep).

The SA 4-42 barrel is also interesting. Your serial # falls into a range of left over receivers that were not finished into complete rifle until the early 40's. There are some serial #'s listed on vishooter's site http://www.vishooter.net/m1903.html that are close to yours with late SA barrels. Particularly 1340xxx with SA 7-42.

Are there any inspector stamps on the left side of the stock? I'm sure some others will have more to say on this.