According to the  Chev dealer local, the problem is crankshaft surface finish. I am surmising that going to a heavier oil, just delays the inevitable failure.

The owner of Willis, is Ford engineer Brian Wolfe. One of the guys who helped start the 5.0 deal way back in the 80's. Brian was the lead engineer on several important programs, as well as a stint as the head of Ford racing, where he got approval for the Mustang Cobrajet program, of the 2000's. He also formed the team that developed the new Ford Prostock engine 2006-2007, that never received NHRA approval, and was never raced. As we know,NHRA, did allow a version of the current "Warren Johnson" based to be used in the Mustangs, but never the Ford engine designed by Brian's team, while he was the head of Ford racing.

Still at it, a .010 shim under the camshaft thrust plate, and removing material from the root of the distributor gear, plus taking the sharp edge off the camshaft gear, adds up to the whole,shebang WILL rotate. Still, IMO the lower, pilot hole is off about .005" though that is a tough measurement to get right.

I'm still at it, shimed out the thrust plate, tried a few thicknesses,  did allow me to get the distributor seated. However still would lock up. The camshaft gear is hitting the root of the distributor gear. So I took my pattern files and worked on the root of the gear teeth. I finally got the whole shebang to turn. It's a bit rough, but it did make 1 revolution, so I could get a gear pattern to look at. Then I decided to try and old camshaft and the Mallory dual point , and locked up tight. This old camshaft and Mallory distributor turn nicely  in the 428 block. I did get a couple drawings, and that distributor hole, is off , closer to the front surface and slightly off the vertical plane IMO. SO that's it. I really have not removed any material from the face of the distributor gear teeth, it's all been at the root, where the camshaft gear has been contacting.  I keep looking at the 428 block, maybe I should change to katz428.

The  whole bore for the distributor hole is off. It would require what Blair is suggesting, unfortunately.  The bore for the distributor, is 0.016" closer to the machined front surface, where the camshaft thrust plate is attached, than the measurement I got from the NOS 428 block.
It would be nice to have a drawing  of block showing the factory dimensions.

It seems that the gear on the camshaft, the teeth are maybe too thick, compared to an older Engle camshaft I have here. I don't know if there is anything that can be done, to correct this. I did see a post on Yellow bullet  where a gent with an Olds engine had a similar problem, the cam was replaced, and problem solved. Yes, I hope, that this block doesn't leak, it was pressure tested, but that was water jackets. Thanks for the feedback.

Yes Brent ,I removed the timing set, checked camshaft end play,  again, then tried the distributors again with no luck. Won't turn.