Very nice! I lucked into a great deal on a Smith Ent/ mount, otherwise I'd have bought the aluminum Sadlak mount. There are so many bad M14 mounts out there, it's nice to see someone put a quality one on a quality rifle! Have fun with it!
You have to remove the stripper clip guide, which requires drifting out a roll pin and replace it with part of the mount. The bolt on the side of the reciever goes inot a hole that it already there. The bolt head is a 3/8" hex head, the same size as the gas plug.
Some of the Springfield recievers were not up to militay spec in some of the scope mounting dimensions. Sadlak sells a kit for around $5 to measure your reciever and if it's not to spec, you send them the measurements you got using the kit and they will build you a mount specifically for your rifle.
Nothing extra, the hole is already drilled in the side of the reciever. The clip guide is removed and there is a tab that you install, and that is screwed in and secured with locktite. It is held firmly with those, and also supported my a screw on the forward end of the reciever for extra support.
It is built like a brick sh**house. I talked to the owner of the shop, Mike Sadlak, for about 45 minutes, a very good guy to work with, stands behind his products.
Heck he even e-mailed me after awhile to make sure I was happy with it.