These guys make an 80%UZI REPAIR SECTION, 80% RECEIVER . Minimal welding needed on your part.
That's the downside of the Uzi. i know nothing about welding.
If you have a real good hand at welding, the same site sells de-milled receiver sections that you can re-weld....
i'll just stick to...
I've been thinking about an Uzi build for a long time.
I hear good things about these peeps' products Uzi Semi Auto Receiver - Fully Welded
Keep us updated if you start building one @Bullet Guy