I would like to be able to put on a slant brake or even an AK-74 style break.  I will use a U.S.-made break + 6 other U.S. parts (furniture + FCG).  

Thanks!

ETA:  I meant SA-85M  Also, there is no 'retaining pin' or whatever it is called to 'lock' a break in place.  Can that also be added?

Thanks for the info!  I figured it would start getting involved.  This was the only rifle he had at the store.  Do you know if there is a muzzlebreak that can be pinned on like they have for the SKS?

Quoted: Also, there is no 'retaining pin' or whatever it is called to 'lock' a break in place.  Can that also be added?

Yes, whomever you get to thread your barrel should charge no more than $7(that includes the parts) to put the little pin and spring in for you. The hole should already be there in the front sight block, it simply needs those 2 tiny parts.
I had my post-ban 85M done this way long ago...

Quoted: Do you know if there is a muzzlebreak that can be pinned on like they have for the SKS?

Global Trades sells a US made slant brake 100% identical to the original one that came on the pre-ban SA-85M's. I'm sure you can find them elsewhere too. They are not marked, so it is actually impossible to tell if it was made in Hungary, USA, or Timbuktu.

If you pull the front sight to put the spring and plunger in, make sure you put an index mark on the bottom of the barrel and sight base; it's likely that the base will go back on crooked if you don't. If you do this, let us know how it goes.