Nice writeup. It all makes sense to me except for the following part.
The 5/16" threaded holes is what you mount the aluminum block-off plate to? Look like the standard holes they put in the Magnum blocks for the lifter spider so that is what block I thought you had until you said it was an X.
Is that 9/32 drill opening the passage from the main bearing to the cam bearing or is that chosen because it is the 5/16 tap drill size? Going all the way through saves another setup to put the threaded holes in from the top and there's no real need for it to go through the top of the bearing. Moot point because a screw will plug that hole.
Do you support the hose T in the middle with a bracket? I know that you use the rubber hose so it will flex, which is good, but that unsupported mass is a potential failure point from the hoses flexing. Fixing that in place will still allow the parts to move due to the rubber hose, but the natural frequency will be raised significantly and that frequency is where you get resonance which will significantly multiply the forces the parts are exposed to. I did a lot of HALT testing (highly accelerated life testing) on industrial automation equipment and motors. This is exactly the kind of thing that we would look for in our design reviews and testing. Not every application will expose the weakness, but some will. If you eliminate the weakness, the customer will be more happy.
Just a thought. May never be an issue in a race motor due to short run cycles, but that would be real liability in anything driven regularly.
One last thing. Anything stopping you from using this technique in a later Magnum block that doesn't have shaft oiling going to the heads? You should be able to drill down maybe an inch through where that passage normally would go to the cam bearing and then bring the line in? It would just be closer to the deck face and drilling an inch is a lot easier than going. About where that lump is?
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