I have drilled them out but I won't recommend it.
They move the weight (balancing) to the flexplate to give you more convertor options. You can use convertors for internal balance engines.
I didn't know they had done that. I couldn't figure out why they list so many different flexplates. There's like 9 different ones on Ati's site.
I could see a few. 3/8" and 7/16", then a combo of 6 bolt and 8 bolt. Now I got it, cause you add in balanced and unbalanced. But why big block and small block? They are the same. :?