Is this a farm or ranch? Are any livestock kept there?
If there are no other conductive pathways such as telephone wires, water piping, gas piping, and so forth that connect the separate building together than you can rewire it just as it is.
If there is any other metallic pathway between the buildings then you must run separate ground and neutral conductors.
In either case you must install a grounding electrode system at each building and use it to ground the building disconnecting means enclosure.
Your new panel would need it's main breaker in either case to serve as the building disconnecting means.
--
Tom Horne
[This message has been edited by tdhorne (edited 05-18-2004).]