Originally Posted by mattface
use a smaller chainring, and correspondingly smaller cog for the same gear ratio with better chainstay clearance.
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.