4.11 is lower than 3.73, not higher. With the double overdrive of the 6 speed, a 4.11 would be a great gear to have. Depending on your tire size, your highway rpm's will be in the 1800 range. That'll give you both low end for stop light to light fun, with good highway rpms.

 

Which 427 crate engine are you looking at? The old BBC 427, or the newer 427 LS based engine? Either will be a lot of power to run through a T56, but unless you're drag racing, or really punishing it, I don't think you'll tear it out the first time you drop the clutch. The real issue will be traction. If you put some big sticky tires under the rear, then you'll probably have issues with the trans. The better your car hooks up, the better chance you'll break something in the drivetrain.
Considering the prices of 12 bolt rears, I'd look into a 8.8" Ford from Explorers. It's Ford's copy of the 12 bolt Chevy, and about 1/3 the price of a Chevy 12 bolt.

 

Well I saw a few different kinds on summit and Jegs. I'm still not completely sure what kind yet. I would love to do 4.11 and a 5 or 6 speed doesn't make to much a difference. I'm not really trying to make this a track car. I would like this to still be a weekend driver to mess around with. Well I'm glad that you guys are helpin me out. I have done some searching and found someone that can take a t56 and beef it up. How much modification is needed to get the ford 8.8 to fit?

 

Here's a good 8.8 build. The only difference if you follow this, is you would need a 7.5 10 bolt from a 3rd gen, instead of 4th, but the concept would stay the same. The torque arm is the most difficult part.

So i Finally bought an 8.8! - LS1TECH