You need to replace the gas block on your STAMPED AKM. The milled AK47 did not use the same bayo lug the stamped ones did. They used the early bayonet that locked on two hooks on the bottom of the front site base where the cleaning rod locked in. K-var may have the gas block you need, depending what make and model of rifle you have.
On a MAK90 you need 5 compliance parts to make your rifle legal. The parts must be US made. You are allowed only 10 imported parts, and a stamped AK has 15, + 1 if you have an imported muzzle device mounted. If your barrel isn't threaded, 15 parts. Milled rifles are 14 + 1. They don't have a separate barrel trunnion, so the receiver is 1 piece instead of 2. Your compliance parts can be a US stock set : 3 parts, US trigger group : 3 parts, US follower and floorplate in your mag : 2 parts, US pistol grip or gas piston: 1 part each. There are also US made clips that are 3 parts. You need any combination of parts count needed. A trigger group and US mag will give you 6 and allow an imported stock set. Most people do a trigger group, gas piston, and pistol grip for a 5 count gun. If you go with US mag parts or mags, DO NOT USE UNMODIFIED MAGS IN YOUR GUN! IF CAUGHT, YOU WILL LOSE YOUR GUN AND PROBABLY GO TO JAIL! $50.00 will get you legal. Spend the money! By the way, if you're in Kalifornia, don't change a thing, it's illegal. As for where to get the parts, Tapco, K-var, FAC, and others sell the parts. Do a Google search and you'll find all you need. Follow the rules, and everything will be cool!