New motor blowing oil on headers

The rings seating will depend on ring type and the finish hone on the cylinders. I can't really help with the damper being hard to install as I'm not familiar with the ATI. I have read in the past where some dampers needed to be honed to get a good fit on the crank, but that's been years ago. Hopefully someone can add information here. If you have doubt about it being seated I personally wouldn't run it until I knew for sure it's correct. The crankcase venting would be something I'd also get sorted out. On the 440 in my Demon I'm running a close to factory PCV and breather system. Breather on one side with hose going to air cleaner, pcv on other plumbed into base of carburetor. There are others here on the sight that are more knowledgeable and hopefully give input. Be patient.