So you have the metal upper receiver and the plastic receiver and barrel? Well then isn't it just a matter of adding stuff up? Are you that lazy? Here's a impromptu list:

Complete V3 mechbox
motor
battery
Hopup and hopup rubber
Magazines
That's pretty much it.

Really? Excuse my ignorance but I thought that there was a bit more to it. Alright, now for the Mechboxes, what kind of prices would I be looking at for Systema mechboxes, new. I couldn't find anything on WGC or Redwolf.

You can't get a V3 Systema mechbox. And you didn't really give a clear answer: What parts do you ACTUALLY HAVE???

If you don't know what parts you have, and don't know what parts you need, maybe you shouldn't be trying to build a gun?

I've got the full receiver set, the battery, the outer barrel. No inner barrel, no mechbox, no motor, no inner barrel and hop-up.

So....you kinda answered your own question there hunh.

Hahaha, yeah, this thread was pretty useless...

Well, where can I find the required parts cheapest? WGC and Redwolf don't seem to have mechboxes, and gunnerairsoft has crappy brands.

huang (read: dragonred) carries v2 and some v3 mechboxes. Carl/Madmax had some for sale at TAC08 as well, but I dont' know if he regularly has them instock or not.

The AK V3 is easier to find. The AUG V3, not so much. Good luck with that.

Get a parts list for the gun you want to "fix". Get every part that you don't have...