I've done research on this. First off if you want the as val the only good option is the LCT. As for the VSS, you can go either king arms or lct. The king arms has had issues with the hop up chamber being too far forward, resulting in either misfeed and bad air seal. If that is the case on yours, you will need to buy a replacement part from king arms. If you want to get the LCT the only downside is the price and the look of it, its a little bit less true to size. Hope that helped your choice a bit. As for parts I believe they use the standard v3 gearbox so its not hard to upgrade.