Got some updates and questions - there's going to be a bunch of pictures on the bottom for everyone's viewing pleasure:
(1) Turns out this isn't an Indian receiver. This is an early-production, likely pre-WW1, BSA receiver. There's also matching serial numbers on the receiver, barrel, and rear sight leaf. Ishapore then refurbished and scrubbed, to an extent, the receiver in 1940. Ishapore is known to have done this - taken early pattern Sh. L.E. rifles from before WW1 and refurb'd and modernized them while gearing up for WW2. The Indian Army went from about 250,000 to 2.5 million during the early stages of WW1.
(2) The barrel has a "H.V. S.C." stamp, which is supposed to indicate that the gun was originally built for MkVI ammo, which was standard issue between 1904 and 1910, but then updated for MkVII ammo at a later date. The barrel also has a "GRI" proof-stamp on it, which is an Indian proof. So, this has a BSA receiver and an Ishapore barrel.
(3) The yellow paint does mean second-rate service. So, this is a functional rifle that was somehow out-of-spec.
(4) "SOUSA" might be "Southern Ohio Guns, USA", but my bet's still on a former owner of Portuguese ethnicity.
(5) With this being an early-production BSA receiver, I'm cancelling the Rhodesian sniper rifle project because that would involve painting this with Rhodesian baby poop paint and also drilling and tapping the receiver for a scope. This now leaves me with three options:
(a) put a sporter stock on but otherwise restore this into a functional Ishapore or BSA SMLE; (b) restore this into an Ishapore-pattern No. 1 MkIII from WW2 with a teak stock; or (c) restore this to an Edwardian-period SMLE, replete with walnut stock.
I would get the most use out of a sporter with a newly-made stock from a blank and this gun is never going to be "right" because of how much it was re-worked over the last, say, 115 years. I could avoid doing any modifications to the metal, such as drilling and tapping for a scope. So, if someone else wants to add on a military stock, they could without any issue. F*ck that shit.
Cloning a WW2 Ishapore isn't ideal because those are relatively inexpensive and common. However, it may be the best option for a stock because there's a fair amount of deactivated Ishapore No. 1 MkIIIs floating around. Deactivated Ishapores are around $120, so I could snag one of those, dump the receiver and the barrel, and harvest the stock, bolt, etc.
Going full Edwardian, with all the brass accouterments and bells and whistles, would likely be the hardest option and requires finding an original (or maybe reproduction?) walnut stock. Maybe I could use a stock blank? Don't know.
I'd prefer to either go sporter or pre-WW1. I'd get a lot of use and enjoyment from a nice, lighter sporter. The pre-WW1 guns also look very nice.
(6) I've cleaned up the outside with Hoppe's and surprisingly most of the crap came off pretty easy. The gun's still going to need to be refinished because of random rust and other defects. But, I want to pick up some sort of spray bore cleaner that I can blast down the barrel to hose out the bore. Brake cleaner? CLP? WD-40? Then run oiled patches down to lube? Suggestions?