I drilled an S1 block once for my Orion. Very easy enough because of the soft cast material. And you don't need a 30mm drill bit. I think I used 16mm as this was the biggest one I had. Then I used a step drill, and a rotary grinder as last. So, basically whatever I found. Was done with the engine in the car in minutes.
Everybody seems to warn about getting it dead right to the correct location. Bollocks, nothing will change if it goes a mm here or there. Even a huge 2mm error will result in less than a degree of timing error.