Yes, the Hi-Lux Optics Malcolm USMC 8x 31mm Sniper Rifle Scope was designed for the M1903 or M1941A1 rifles.
No. This is designed to have the front block mounted (drilled/tapped) to barrel through the handguard of a 1903 (not 03a3). The rear mount will have to be drilled/tapped to front of receiver where the make/serial is. Major modifications to the rifle are needed.
No, you must drill and tap the receiver and barrel to install this.