So, you want to build a BM59? It sounds easy, but first you need to figure out exactly what you want in order to avoid wasting time and money.
There is scant information out there for the BM59 builder/owner. One of the better places to start your research is the Battle Tested forum. They have many BM59 owners who have posted many photos of their rifles and parts.
Battle Tested can be found here:
http://forum.shuffsparkerizing.com/forum.php
Battle Tested forum will require you to register in order to see the photos and access some of the private areas of the forum. There is also a lot of info on Garands, carbines, and other US military arms. It's a spin-off of the Shuff's Parkerizing site, so don't be surprised to see lots of info on Shuff's.
I had my first BM59 built several years ago before all of the parts kits came into the US. It is what is known as the BM59e. It is essentially an M1 Garand with a box magazine and flash hider. I'll start with this rifle model for those that are thinking of building one.