A lot of the stamped bolt housings show the cleavage at the bottom. I think it's caused by the manufacturing process when they stamped and rolled the sheet metal. I have a few of those and they are safe to fire. We need to see a picture of the back of the bolt and a close up of the front sides of the firing pin carrier below the oval hole, also a picture of the front of the the bolt carrier where the actuator rod strikes. Those are areas of concern that require close inspection for cracks.
With an all matching rifle like yours an extra $300 - $500 should be set aside for buying a replacement bolt carrier, bolt housing, bolt and firing pin carrier to save matching number parts from accidental destruction. New springs are available for about $15 on fleeceBay, shooter kits can be ordered from Rob Applegate at apfeltor.com or look for seller allibaba34 on fleeceBay.