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Not all swaybars are spring steel. Many of them are simply 4340 shaped and then hardened. Since hardened steel is just about as hard to drill as spring steel you might try this trick to drill it.
Heat the area you are trying ti drill with a torch until it is a dull red hot. Be careful not to heat more of the bar than necessary. If this is a heat treated bar, the heat will take the temper out of the area you heat and you will be able to drill it easily. I've done this a couple times on parts on my roadster during the build and it worked perfectly. Yeah, I hate going through expensive bits too.
Another option is to not use a bolt, use one of those half round cradle type connectors for your sway bar that clamps to the bar and has an attachment part on it. No holes needed in the sway bar.
Bob
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