I'm not conviced that Dredge is the best place for Laboratory Maniac. The same hate that keeps you down games 2 and 3 will stop you from milling your deck. While Maniac gives you a more-resilient game 1 win condition, it doesn't really improve the post-board matchups.
That being said, I'm sure Maniac has a home somewhere...
If not dredge, his home is built out of one of the following:
Oath
Leveler
Mirror of Fate
Thoughtlash
Demonic Consultation
Divining Witch
That-one-white-dude-who-mills-for-more-white-cards.
I put my money on Mirror of Fate. It's a win off Tinker if they can't address Laboratory over the next turn, and it only requires 2 slots in your deck.