These 3 Savage FAQ articles should tell you what you want to know.

Bolt Tear Down

Extractor Removal/Install

Ejector removal/Install

The only difference in a RB/RP 4.41" spaced Target Action with a .473" vs. a .378" bolt head is just that, a different bolt head.
You can often buy the bolt heads from Midway, Brownells (I think), or possibly from Savage if you can get them to let you if you sign their liability waiver. PT&G also makes aftermarket bolt heads that I am told are high quality.

If it were me I would become a Paid Member here and put up a WTB thread in the classifieds, I would be willing to bet that another member here would trade you a .378"-SA head for the .473"-SA head that will come on that action.