It appears I had way too much timing in it, and it was detonating. Some of that likely had to do with me not understanding how to properly set timing, plus I think my old dial back timing light is way off. I bought a new light to check that out and set the new build. Both machinists at my shop agree from plug inspection and checking my distributor and vacuum advance. Most of the rod bearings had lost their crush but the mains are still OK.