I could help you out. I've done a few conversions of this sort before. I think your cheapest/easiest option would be to mill the rail and tabs flat. Then, drill and tap both the front and back of the feedport. The standard phantom feedblock can be modified with a second mounting hole to mount either forward or backward. PM me if you might be interested. I can also mill the radius for the vert adapter without a problem. https://sites.google.com/site/lexion...s/DSC01736.JPG https://www.mcarterbrown.com/forums/s...ing-build.html
It would be like these two but without the radiused body.
PM me if you are interested. We can discuss a few options and price.