What he's trying to do - I think - is swing the valve events around to close the overlap. Some engine builders think that most people have never had a "de-tuned" engine re-converted to lenthen the power band. Most gernade because they won't take wear, which is figgured into most grinds available today.
I had a like same problem with a "friend" that was trying to convince me of the same thing until I noticed what he was doing......which was strech out the clock & produce a STOCK overbored engine from the 60's. I wasn't impressed with them then, so I knew I wasn't going to like it now & that he was WAY off base to what I wanted. I ended up taking the engine back from him & redoing it myself to what I wanted.
You can run 10:1/2 to 1 on pump fuel. I do it everyday & without ping. So your ok there- as for your hp, as a guess ( there are others here with the equations in their heads) I would say from your descriptions that you may get 475-525 max. He is using quality parts, and there is nothing wrong with that- but it's taking a LONG time to get it back.
Good Luck......and you may want to invest in some stock from Shell Oil.