Well, here's what I have from the photos I've seen so far.
First off, very nice Carbine! I'm jealous. It should be a late-war Rock-Ola that was subsequently arsenal rebuilt at some point. It is in one of Rock-Ola's later serial number ranges.
So, here's the parts I could identify from the photos:
The rear sight appears to be original.
The bolt may or may not be correct. It's the correct type, but would want Rock-Ola stamped on it somewhere. When you get it out, check the firing pin. They stamped those as well!
The barrel appears to be correct. Rock-Ola stopped stamping dates on their barrels starting in 6/43.
I can't tell the front sight from the photos.
The front band is not original. It's actually an Inland and Rock-Ola never made any with bayonet lugs, as far as anyone knows.
I don't believe the Operating Slide is original to the carbine. It's a Type 3 and you should have Type 4. Check it for stamps, though. They usually put them inside the belly of the opslide.
The trigger housing appears to be correct. It should be the stamped type with some brass brazings on it in places.
The safety and magazine catch are not original to the rifle, nor is the stock. The stock looks like a pot belly stock to me. Check the left side of the stock where the receiver fits in for a relieved part where a selector would go.
The handguard is from the Inland Division of General Motors.
You want an oiler stamped with IR on it if you can find one!
Hope this helps. Almost every part on the Carbine is stamped somewhere. Some of them, you have to really disassemble it to find them. Hammer, firing pin, sear, etc. Even the buttplates are identifiable! A Rock-Ola would be missing a diamond at the 3 o'clock position by the screw countersink. Seriously.
Hope all this helps, and congratulations on your find!
Cheers,
kk7sm
ETA: On second glance at the photos, I can see the selector cut-out clearly visible on the stock. That cut was put in the stocks so they could use the same stock on the M2 Carbines with the go-fast parts.