I'm not remotely qualified to answer the welding question, but what about hardening one of those mild steel blocks with Super Quench? You can find the formula here on IFI, and it's going to cost you a LOT less than the welding consumables. Even if it doesn't work, you've only wasted one block out of your stash. Might be worth considering.
Oh, and if you want something of comparable mass, you could weld two of your 95 lb. blocks together.