The squeak almost sounded like a loose side pipe rubbing or something to me.
As for the
oil pressure, 100 psi at cold startup isn't going to hurt anything. I don't like
oil pressure that high, but the fact of the matter is that when it's good and hot, it will be 20-30 psi lower.
Be sure and check the timing. MSD boxes (if that's what you have) can read differently from box to box, so even if the timing was set on the dyno, it could be different now.
If it's a hydraulic cam, the chatter you heard at the beginning could be the engine running before the lifters pumped up.