My GP1975 came with a Tapco buttstock and an unknown synthetic fore end. Take this with a grain of salt, but since we have similar receivers, expect some fitting on your end. The folks at Century are not comparing their guns side by side to a well fitted AR so they seem to get them out the door "good enough"...
Completely disassembling my gun, there is extensive rough filing to make the stock set 'fit'. My buttstock's holes are a little hogged out and casue the stock to shift forward and back about 1/16". Kind of annoying because I put considerable tension on my sling sometimes mounting the gun and it constantly shifts around.
K-Var, agreed, is the "decent" one I've seen but a bit more expensive. I expect to need to do some fitting when I pick up one their stock sets as well.
That being said, the AK is a really fun platform to run. It's really easy to get caught up in decking out an AR with ambi-this and big latch or extended-that. The AK platform has done wonders for my efficiency & appreciation of how well engineered the AR is bone stock.
A little $$ goes a long way with one of these guns too so enjoy it.