[lopaka311]

I have the opportunity to get a second gen rear end with disk brakes.... so What would have to be done to get it to fit under and attach to my 1972 dodge crew?

Both my current and the second gen are 411 dana 60's

 

[u2slow]

Here's how I did it with a drum 2ndgen axle on my '93:
https://ramchargercentral.com/axle-tech-discussion/dana-80-swap-westcoast-style/

If I was to do the same with discs, I'd change to a disc/disc prop valve and re-invent the parking brake connection.

 

[lopaka311]

If I read that right you put a 3rd gen in a first gen. which is helpful tells me it can be done. I'm more or less asking what needs to be modified to fit a second gen rear under the first gen as far as hangers and anything else Brakes are a given since it would be to disk brakes.
how much wider/narrower is the second gen are the hangers at the same width apart etc.

 

[SuperBurban]

You might need different rims. Either more offset, or even larger diameter rims and tires. I passed up a nice axle, because I would have needed 18" rims and tires.

 

[u2slow]

If I read that right you put a 3rd gen in a first gen. which is helpful tells me it can be done. I'm more or less asking what needs to be modified to fit a second gen rear under the first gen as far as hangers and anything else Brakes are a given since it would be to disk brakes.
how much wider/narrower is the second gen are the hangers at the same width apart etc.

I used a '95 (2ndgen) Dana 80 SRW. Its about 5" wider that the 1stgen SRW axle.

The spacing of the perches, hangers, and frame width are the same 1st vs 2ndgen. What changes is the spring width from 2.5" to 3" and length from 52" to 60".

Most guys swapping to the 2ndgen axle keep the 1stgen leafs. 1stgen ubolts plates (for the 3.5" tube D70) should work on the 2ndgen D70 for the shocks.