Oil for Rebuild

Hello All, As I will hopefully get my short block 144 back this week, I'm wondering what the opinions are on oil for a newly-rebuilt engine. Natural? Semi-Synthetic? Other? I normally run Valvoline 10-30 semi-synthetic with good results, but didn't know if break-in is different.

Yes, break-in is different (short run - 30 min @ 2,ooo rpm or less?) requires a hi ZDDP oil. It gets drained right then - look in pan for metal filings beyond the norm, cut open filter if showing 'chunks' & examine that 'byproduct' (frm inside filter). Some use "break in oil", I have less expensive (Luckas I believe) additive mixed to each qt as it goes in that 1st running/starting/tuning. If going that more expensive route - Brad Pen is used by many here.
After that (usually 1st 500 mi of test driving) again change oil. This 2nd fill is not w/'break-in" oil, but continue close exam of what's drained. Some use 10w30 (some still want the 'zink' additive often for the duration, not I). 10w30 winter/10w40 summer, 3 - 5,000 mi changes thereafter…

Do U have 'hardened seats"? What rings?

Many opinions, but that's one.
Let us know how U go...

Excited about picking up the motor today...hopefully no Snafu's. I don't have hardened seats, it's just a weekend driver. I'll have to ask about the rings, but it was just a standard rebuild with no upgrades as far as I know. I had the head done about 200 miles ago, and this is just the short block. What I liked about the valve job was that instead of sleeving the guides, they drilled them out and put in oversize valve stems. Hopefully this weekend I'll have some updates and pics.