'cb1' - You have the makings of a good utility & hunting Krag.

You will want to repair the Stock cracks by working in some 'Accra-glass' (epoxy-bedding) compound.

Clean the metal using a rag with kerosene, mineral-spirits, or denatured alcohol. (A good soak can help).

Light rust can be improve by lightly rubbing with #0000 steel-wool saturated with Hope's #9 solvent.

Heavier rust deposits sometimes respond to bronze brush or edge of a copper penny. Soak rust area with linseed oil and work rust patches with brush or coin-edge. It makes kind of an abrasive 'slurry', that should be wiped occasionally with paper towel, then re-do with clean linseed oil; (I sometimes add a little rotten stone to the linseed oil). Check your progress as you go along.

The goal is to preserve original finish and age patina. Avoid harsh abrasives, emery cloth, wire-wheels, and naval-jelly!

It's an old gun. You want character, not 'new'.

Your rear sight is a commercial 'Pacific' K2 (manufactured in San Francisco from approximately 1928 to 1953). A lot of people like the 'micrometer' K2 version.

No SRS 'hit' on #293653.

(p.s. - I was responding at same time as 'Rcat'. I was not questioning his method).