I picked up a SR Apex crank with 86 bcd chainrings from eBay. The crank and rings are in good shape but the crank bolts are seriously stuck and rounded out. Someone overtightened these. I reckon the best way to get them out is to drill them out.

Any better ideas?

Also what about replacement chainring bolts? There are plenty of chainring bolts for a double crankset but these need a longer chainring bolt as the same bolt is used for all 3 chainrings (unlike a 110/74 bcd triple). I take it that I'm going to have to look for used chainring bolts? The bolts are 12 mm in length and chainring bolts for doubles, which are readily available, are right around 8-9 mm in length.