You have two choices on stocks.
One is to install a lower tang.
You can buy the tang from Global Trades.
You may need to cut a slot in the lower inside of the receiver stock socket, then the tang can be either riveted in place or attached with socket head screws and nuts.
Tang:
http://www.globaltrades.com/ak_stocks.html
HOW to install the tang:
http://www.gunsnet.net/forums/showthread.php?t=110911
Your second, and easiest choice, is to buy a new stock from Ironwood Designs.
He makes a special stock specifically for the single tang milled Bulgarian receiver that uses a square nut and a stock bolt to attach the stock.
This is a simple conversion that is simply screwed on the rifle and is quite sturdy:
NOTE: Ironwood is currently trying to catch up with orders and isn't answering emails too fast:
http://www.ironwooddesigns.com/
I STRONGLY recommend you NOT simply install a standard AK stock without a lower tang.
First, there'll be an ugly slot for the lower tang that will be exposed, and a good bump will knock the stock out of the receiver socket and break the top tang off. THEN you have problems.
On the muzzle attachment.
If your SLR already has the factory muzzle brake, it's one of the most effective, so I'd leave it alone.
The slant break is really only effective in full-auto fire, and on a semi-auto is mostly a matter of appearance.
If it doesn't have a factory attachment, the "best" option is to thread the muzzle and screw on whatever you want.
On some of the gun forums there are people who will rent you a threading kit complete with a special bore guide that insures straight threads.
Threading the SLR works very well, and is easy to do.