Yes, I agree with taking measurements for sure, but I think you will find late model rear will be too wide. You can have it narrowed, but depending on axle availability, the cost starts to get up there.
Custom width 9" rears are another option, but very pricey.
For my 59, after some research I decided on a F*rd Explorer 8.8 with disc brakes, limited slip, 3.73 gear, 31 spline axles, 3200lb axle capacity, and 1/2" difference in width, which I found readily available used locally for around $250.
Google "8.8 ford rear end" and you will find sites like this:
http://www.therangerstation.com/tech_library/Axles.html Gotchas with the "Exploder" 8.8 are that the pinion is offset from center (3" if I recall) and the bolt pattern is 5x4.5.
I've read the offset pinion is within normal limits of the u-joints.
For the bolt pattern dilemma, I’m going to go back to Fatman’s and swap them my hubs with a Chevy pattern (on my IFS Mustang II kit) for F*rd and all will match.
