The selector is a part from the 922R list.
The 16 countable parts of an AK rifle. No more than 10 of these parts may be imported.
(4) Muzzle attachments*
(6) Bolt carrier
(7) Gas piston*
(12) Pistol grip*
(13) Forearm handguards*
(14) Magazine body
The parts with the * are the most commonly available U.S. manufactured parts.
On a typical stamped receiver rifle you need to replace 5 parts with no muzzle attachment and 6 parts with a muzzle attachment.
On a typical milled receiver rifle you need to replace 4 parts with no muzzle attachment and 5 parts with a muzzle attachment, because there isn't a barrel trunion, it is part of the receiver.
When building an AK pistol, these regulations do not apply. You can not have a stock or forward pistol grip on a pistol.