Okay, I've been doing some research, and here are the potential issues with the CZ-USA imports.
On the Tactical Sporter and Military Sporter models, there is only one OEM magazine. It uses two 922(r) compliance parts (follower and floorplate). This means that using a military surplus magazine with one of the CZ-USA imports is a violation of 18 U.S.C. 922(r).
On the Military model, three of the foreign parts are the buttstock, pistol grip, and the handguards. In other words, four parts count as three. OTOH, the Tactical Sporter poses a problem. Here, three parts count as three parts. That is, the tactical stock counts as a buttstock and a pistol grip, and the handguards as one, for a total of three. On the bright side, if you were to buy a folding stock kit, it can't hurt you, because you are substituting a Czech part for a Czech part.
Back to the real issue. If you want to use military surplus magazines here are your options.
Remember, you must replace two parts on either version.The most practical solution is probably a US made gas piston and a US made pistol grip. Obviously, this idea works a lot better on the Military Sporter model, because a pistol grip can be changed without changing the buttstock. For the Tactical Sporter, the most practical solution seems to be a US made gas piston and US made magazine floorplates (install these in the military surplus magazines).
The muzzle attachment/barrel extension is a real problem for a CZ-USA import. The vz-58 has to have some sort of fixed barrel extension, or it is a short-barrelled rifle and a NFA violation. When you build a vz-58 from a kit, it is pretty easy to get a US made muzzle attachment, and weld it to the barrel. This is not a violation, because you do this before pinning the barrel to the receiver. In order to legally go this route with a CZ-USA import, you have to have someone with a manufacturing license do the work. Alternatively, you may be able to remove the barrel from the receiver and change the barrel extensions. I am not sure on the legality of the latter option, however.
By the way, the US made floorplates are nice, but the US made followers are pretty substandard. They don't even have a ridge or clip to secure the mag spring. I would avoid the followers for two reasons: 1) poor quality; and 2) $6 each.
I almost forgot. US made wooden stock sets are also available. These count as three compliance parts.
Source for U.S manufactured vz-58 gas piston:
http://www.gunco.net/forums/f259/usa-made-vz58-pistons-37547Source for US manufactured pistol grip:
http://www.lichtenbergresearch.com/parts/vz58pistolgrip/vz58pistolgrip.htmlSource for U.S. manufactured floorplates and followers:
http://www.tnguns.com/shop/index.php?main_page=index&cPath=42&sort=20a&page=2Source for U.S. manufacured wooden stock sets:
http://www.prexis.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=P&Category_Code=VZ58
