Also, I would take a few thousands of the OD of the dist gear, to make sure it isn't bottoming in the cam gear.

Just a thought, if I was going to take the .016 off the front of the cam, I think I would try it with an old junk cam first to see it it works

       with rollers always set to the tight side-- never loose-- some cam techs. will tell you a fairly large range tighter--set too loose and pound a roller is a good way to hurt engine--bad !

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.

Maybe a little late but I would look hard at a Prime Weld Machine or CK. I bought the Prime Weld Tig225 and it will do about anything you would ever want to and the price is very reasonable. They are good machines and use CK torch/lead and quality parts.
I will say as a novice, the knobs and settings re a bit more complicated than a machine that has auto adjust but you are getting a lot of machine for the money capability wise. I found pulse to be awesome doing some 1/8" AL boxes. Another machine is CK Worldwide. From a lot of research I feel like for the money both of these are machines that were affordable to a hobbyist, but yet as capable as about any pro would need.  Attached some links that may help.


https://www.youtube.com/watch?v=-YkWY3nVAlY

https://www.youtube.com/watch?v=pfORi2F7xWA