If you put a mic on the average -6AN hose, it doesn't get .375". Then, the fittings are often much smaller than .375". There are some exceptions on the hose, if you are using some of the high end XRP hose it's a true 3/8 or even a little bigger. Very few people use that.
If the 2nd feed line comes in right above #1, but #1 is not isolated from the other mains, then it's not a direct feed. It's a shared feed. The 2nd line does offer benefit, but it's not direct feed.
All the front feed does on the R block is prevent you from having to create your own front galley feed on the right side. That is helpful, but it doesn't really affect the system beyond that. Personally, I believe the dual feed will alleviate the various feed issues we have discussed, when combined with restricted lifter bores and cam feeds. By itself, I don't think it would be enough.
All of these various fixes work to make the engine oil better, and it shows in the fact the engines last. IMO, the single fix that makes the big difference is getting the lifters shut off from the galley....each one can leak a lot and there are 16 of them.
