Just remember if you convert a pre-'65 rearend to 5-lug,... you will need to swap out the spider gears to use the new 5-lug axles.
This adds to the cost of things.
http://www.performanceonline.com/196...IDER-GEAR-SET/
Might be cheaper to start with a 65-69 housing (if you want the narrow version),... or a 71-72 housing, that is 5-lug already.