If you know someone who can narrow it and weld the housing ends on correctly, you can come out WAYYY cheaper than buying an S60.
Both of our road runners have cut down truck Dana 60s under them. Less than $1k in each one. Bought all the parts from Dr. Diff.

They will most likely come w/ either 4.10 or 3.54 gears and hopefully you'll get the good powerlock diff. Then all you need to do is narrow the housing, weld on pass. car ends and spring perches, and buy axles. Possibly buy a yoke too depending on what it comes with.
One of the ones I bought came w/ a 1350 yoke, 3.54 gear and powerlock diff.

I paid $125 for one and either $150 or $200 for the other if I recall correctly. Both were complete take out units w/ full floating axles, brakes, etc.