Re: Replacing lead Keel bolts
Most cast in place bolts are just threaded rod, with different designers preferring stainless others like hss steel, and there is a small faction switching to other more exotic materials. For replacement though there really isn't a good option except melting the lead away from the old bolts, and replacing them with new. Frankly a hex head bolt cast in place is a pretty poor option. The head has pretty minimal surface area compared to T or J rod, which increases the problems of point loading.
As for material, it really depends on what you are looking for. A quick cheap fix to get back on the water, go with steel.
Arguably better is stainless, but in keel bolts it has a lot of problems.
If you want to fix it once and never worry about it again, titanium.