[Karl Wolf]

If you're running a hotrod cam, the reduced base circle will make it a bit more difficult to use the wrenches- maybe impossible. The lifters sit lower in the bores. Some people relieve the tops...
Sounds like a lot of work now, but I would consider pulling the crank so as to be able to clean out the drilling proceeds from the lifter bores...

I drilled mine, next time I will put in the cam and a lifter to determine where I want to have the holes at the inside of the bores- make a jig and drill from the bottom... If that's practical...

Karl