I see a LOT of rust. I'd begin with oil and OOOO steel wool and smooth every surface as much as possible. I'd apply oil to the toggle pins and camming surfaces and work them by hand until I was satisfied that they move freely. Remove the firing pin and do the same for it and the channel it rides in. Smooth the inside of the receiver forks if there is any rust there and the sides of the toggles.
IOW, smooth every contact surface. Just don't grind on anything. Let us know how it goes.
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