The original Skorpion was chambered in .32 Auto, which made it a very controllable machine pistol. 9mm Mak is "harsh" compared to either .380 or even 9mm, so I believe the Skorpion will be less "smooth" to shoot in Makarov. On the other hand, you're talking about an SBR instead of a machine pistol, so that changes things. Compared to a Makarov pistol,
anything with
any type of stock should be pretty neat in Makarov.
The gun's upper is sheet metal, so mounting any sight on that won't be so good, unless you could attach it to the front sight itself - the front and rear sights are on reinforced parts of the upper receiver, so they're fairly solid, but they're not exactly removable either.
If I were to find an original-design Skorpion (either in .32 or 9mm Mak), I'd personally want it as close to "stock" as possible, since I think the design is really cool, but that's just me.
Added:
Here's some
good stuff on the gun itself from Steves Pages. If you can find the VZ-61 in .380 instead of Mak, I'd go that way, unless you have access to all the Commie stuff you want. Makarov ammo hasn't been terribly consistent from one manufacturer to another, at least in my experience. Going with S&B, GECO, or PPU has been fair, but the other brands have been iffy...