Welcome fellow new owner!
On the OEM finishes for the Phosphate and Oil items (hinges, latch, hood springs, etc), shop around your area to see who may provide the OEM finish, its not a hard process and usually pretty cheap from what I see (its a bit pricey here in Oz). If you have access to a media blaster clean them to spotless that way, it will slightly alter the final finish from factory stamped, then blow clean with compressed air immediately before delivering them to the shop (if you go that route). Avoid fingerprints, handle with gloves or clean rags!
The Cast Blast is a good product, I've used it a few times, but does look "painted" as is a bit dark for my liking if you are really going for "correct".
It will last longer and provide less maintenance issues (reoiling) than the correct OEM P&O (S2) finish.
The engine will be the same as any other for the time/plant so look about for general restortion info, this area is not specific to the Cal Special.
Enjoy!