Ok, my bushings finally came in and I got them installed.
It looks great and feels like a real gun now.
I ended up drilling the holes to 7/32" and I let the bushing thread its way in. Start with a smaller bit and work your way up. You need to constantly check the location of the bushing holes in relation to the holes in the grip to make sure everything is lined up. If you figure out that the hole isn't in the right place, you can always try to fix it with one of the smaller bits. I put JB Weld on the threads and around the flange of the bushings to hold them in place.
Here's a pic of the finished product before I applied the JB Weld (didn't want to wait to have to wait to post pics).
If you try this mod, do yourself a favor and slightly countersink the holes to make the bushings easier to start.