DANA 60 - Question/Help

I came about an ad stating:

I have a Dana 60 for an A-body that was built to be a direct replacement drum to drum and spring pad location. It has a 3.54 ring & pinion,trac lock posi unit,New Yukon 30 spline axles with green bearings installed,4.5" bolt pattern. It has backing plates for 10" brakes, u-bolt style front yoke and a chrome cover, Ready to go just add brakes and oil.
Measurements ,best I can get with a tape measure are as follows
Drum to Drum/where wheels bolt to axles 57 1/8
Flange to Flange/where B-plates bolt on 51 3/8
Center to center of leaf spring pads is 43"

What do you guys think its worth - going on the seller's statement above?

Best I can guess its from a truck - 30 spline axles. Do you think this would be a good deal for my Duster and would it hold up to the "eventual" big block I plan some day to install?

Waiting for pictures from seller.

Please be honest I'm trying to figure if I should pick it up this weekend or pass on it.

Feel free to PM me.

Thanks