[Richard]

Being the redneck I am, I wouldn't pull the bolts. Carefully drill a hole and just kiss the bolt with the bit. I would use a very small bit, maybe 1/8 or so. Then counterbore with the appropriate bit to tap for the zerk. I wouldn't do this for a high speed bearing or bushing at all, but a small burr in a high load low speed bushing wouldn't be an issue in my way of thinking. Of course flush the hole thoroughly so that you don't force any shavings into the bushing.