I find a lot of good deals with AK's that have underfolders rather than a nice NJ legal stock. If I purchase the AK and then replace the furniture it kind of ruins the bargain. I like the look of the extended underfolder also. Can they be pinned and made NJ compliant? I want to make sure and get this right. The underfolder AK and Uzi are the poster child for the NJ law.

underfold can certainly be pinned, and there is plenty of metal to drop a weld somewhere inside too. 

 

On calguns they do it with half cut pipe wedged in the spring loaded mechanism of the folder with a clamp to stay secure. if you want a step further would be just welding a similar block between the rear trunnion 

Definitive also came out with an UF to fixed stock adapter if you don't like the UF.

Its a bit of a PITA to pin an underfolder but not a big deal, we have this in stock and its NJ legal.