383 rebuild - kinda whimpy on the dyno?

Looks to me like those two cylinders pounded the bearings. Spots on the back of the bearing and the spalling on the wear surface. Oil clearance and flow was probably fine because it’s not welded together. Good catch. Buy some assembly tools and fix it.
And BTW get the right springs for that camshaft before that goes away too. Not enough is bad. Too much isn’t.