My customer is wanting her service changed from a 3 wire system to a 4 wire system before she buys a condo. All the sub panels in the complex stem from the main disconnects at front of building. Would this require changing all the meter housings to 4 wire, or can I check into bringing a 4 wire system (ground) to just her location? I would think that the meter blocks (6) would need to be replaced for All the units, right? Or can I derive a grounding means back to the disconnect?