Make sure to permanently attach the barrel extension first (pin/weld), then put the stock on second. As long as the stock is not installed at the same time as a barrel <16", it remains Title I and no forms or stamps are necessary.
Also, because you are constructing a rifle, you will have to ensure compliance with 922(r) during the conversion. I'm not sure how many foreign parts are in a Draco, but there is probably a list somewhere. Because they are imported as pistols, they do not have to meet 922(r) like imported rifles do, so it's likely that they would have more foreign parts that need replacing.
As mentioned, because the Draco started life as a pistol, it can be freely converted to a rifle and back whenever you want, so long as it is never in an SBR configuration (stock installed with short barrel). Again, no forms necessary to do this.
ETA: Here's a useful 922(r) calculator for AK's.
http://gunwiki.net/Gunwiki/BuildAkVerifyCompliance
If you already have a Tapco FCG (easily verified), you would only need a US-made gas piston, muzzle device (if applicable), and pistol grip to be compliant. If the FCG is not US, you'd need to replace that too.