I'm probably a bit late to the party by I bought a factory CZ Lux stock from the US a few years ago and tried to bring it in via Australia Post's "ShopMate" service, as CZ would only ship to a US address.
Don't ever use ShopMate!
https://shopmate.auspost.com.au/They refused to import the stock, claiming it was a "gun part" – despite the obvious (it's a piece of wood). A lot of correspondence was exchanged, including an official complaint that got me nowhere. In the end, I had the stock shipped to a friend in the US who shipped it via USPS – and it came in via AusPost anyway. Go figure!
So my only advice is, if you're going to import a wood stock from the US, use a courier service or find a friend to help.
There were no issues with Customs BTW, so a long as you can organise freight, you shouldn't have any problems.
The laws of physics do not apply to politics.