you cant drill it, it's case hardened, so i was told??
but if you can follow this its not too hard, mine is a 450r but the mounting for an ex is the same................
i just took my 450 shock, and all old bolts and nuts with me to the hardware store, and whatever ya get,try to get stainless stuff, i did, now it'll never rust, and buy a few extra of the washers , dont make 2 trips like i did,
you'll need a smaller diameter bolt for the top, to fit thru the smaller hole in the new shock, you cant drill it, it's too hard of steel, and washers to match that bolt, like 4 or 6 washers for the top, and then the hardest part of the whole install is that you have to make some kind of bushing for the holes in the top mount, i used like a 3/8 or 1/2 inch brass copression coupling thats used for connecting 2 pieces of copper tubing, discard the 2 parts (nuts) that turn, and just use the middle piece, i drilled that out to the size of the new bolt, then put a bolt and nut thru it, kinda tight and spun it in the drill while holding a file to it, till it fit inside my shock mounts on the frame, then cut it to the thickness needed to fill that mount,
the bottom mount only needs the aluminum shock mounts to be drilled to fit your stock pin that came out, dont drill it too big, make sure you use the right size drill bit, or you'll get play in it, and this whole project goes way better with 2 people, i had a hellava time by myself, cause when you take the old shock off, the whole assend falls onto the swingy, i had to make a brace outta a 2 by 4 to hold the ass up while tryin to get this all together, better yet would be to hang it with a tie down strap from the garage ceiling or a tree limb if your outside, cause it try'd to fall and pinch or cut my damn hand off a couple times, it took me a good 4 hours to figure this out and get it done, but you have a good headstart with these directions,