Originally Posted by Aeroplane
Changing the ratio won't keep the crankarm from hitting.
There are bottom-bracket spacers out there. They will work as long as the non-drive side will have enough room to clear when you put it in.
A punch relief is a good idea, but I'd clear it with your shop first. Nothing worse for a bike than a dummy with a hammer.
Safest way is to just get a new, longer BB spindle. But that might throw off chainline. Tread lightly.
Oh, I misunderstood. I thought the problem was with the chainring not clearing. Phil, and Miche BBs can be adjusted a couple MM either way, but that might screw chainline. A different crank might place the arms out farther without moving the chainring out. If it's a road crank you could use a bb to put it out about 3mm further, and use the inside of the spider instead of the outside.