of your posted lists, the first one has 61 cards with 30 mana sources plus 3 Metalworkers. This is a LOT of mana, and i'm not convinced that you need it all. To get to 60, perhaps cut the Voltaic Key. You said you're not playing that list right now, so I'll skip the rest, but i will say that other lists you posted are better than the first one.
I like your second list better. You are running 28 sources, and i think you can drop to 27, but only if playtesting shows that you can still get what you need. For testing, I would suggest dropping 1 Forest in favor of a 4th Taiga. See if your mana curve is still good.
Also, since i'm a fan of Mana Crypt, I think you can benefit from the acceleration offered by it. You can replace the Grim Monolith. Since you are running Welders, you can get rid of the crypt at some point, in exchange for a creature in the graveyard. I understand that Grim Monolith gives you a place for your Su-Chi mana, but this is an aggressive deck and your opponent should be pressed against the wall as much as possible. Dont worry about the mana. Just crush the opponent.
In the 3rd Deck, Damping Matrix will shut off your Metalworkers. While i do believe that there are times you can play with cards that shut you down as well as the opponent, this one seems too harsh in the deck (especially since you are not playing Welders here).
MUD is an excellent deck (originally designed by Thug and Tindemans).
Here is a link to the Archive Primer:
http://www.themanadrain.com/forums/viewtopic.php?t=11690and here is a link to the MUD articles on StarCity Games:
Part 1:
http://www.starcitygames.com/php/news/expandnews.php?Article=5930Part 2:
http://www.starcitygames.com/php/news/expandnews.php?Article=5943Part 3:
http://www.starcitygames.com/php/news/expandnews.php?Article=5975This info should give you everything you need to make a mono-brown version. Use the primers to decide on a deck-base, and then look at the new cards available and try to make the deck better.
In the meantime, if i had to choose between the 3 decks you posted, i would play the second one, making the changes i listed above.
dave.