New factory S2000 shortblock, break-in oil

I’m based in the SF Bay Area so the climate is pretty mild. Currently in the 50-60s in the day time when I plan to operate the engine initially.
Honda recommends 10w30 conventional for life. No reason it wouldn't work. My s2k had a rebuild about 30k miles ago. Bummer for me is the RMS started to leak after sitting for a year or so. Not bad enough to tear into it but it is annoying. I always wanted a Spoon engine, just to say I have it.
For S2K, reach out to John at LHT Performance in Pinellas Park, FL. He is an S2K master.

He can confirm but I would run conventional for 500-1000 and dump it for synth. Change it frequently going forward.
Engineers usually suggest that you break-in an engine by not being too easy nor too hard. Either method has the potential to cause problems.
There's an old motorcycle video where engine builder always breaks in the engine on the dyno. His theory if you run a new engine slow the rings act like a course file run them up to high RPM the rings act like a fine file. This is how they break in racing engines straight to the engine dyno