Re: Keel Bolts
Ajay, when you mention your next boat, bear in mind this boat will be worth substantially less when the next buyer sees there have been keel repairs. No matter what you say or why, simply having keel repairs changes the value of the boat and raises a question of "why" and "what's wrong".
I can't see any reason to do substantial job like this when there's apparently nothing wrong with your keel as it is. If you don't trust the design and construction, sell the boat now. If you are worried about crevice corrosion failure, have you replaced all the standing rigging yet? That's far more likely to fail, because ccf affects damp parts and keel bolts are usually totally dry inside the keel. Only the tops, easily visible, are subject to ccf from dampness in the bilge.
I also would prefer J-bolts to lag bolts, but consider that lag bolts and lead shields ("Rawl" plugs, etc.) are also the standard way to attach almost everything to exterior masonry walls. All sorts of heavy stuff that gets ignored for fifty years, and those lag bolts hold, assuming they were properly installed. I used to shoot some gasket sealer, the black tarry stuff, in before installing the bolt to ensure there couldn't be any moisture penetration.
Just saying, lag bolts have some track record when applied in lead.