OK, regarding the use of another panelboard interior, let me ask about this stiuation;
At a local school here, there was once in service an old Frank Adam Fusible lighting panel - the kind with heavy duty tumbler switches next to each fuse. Come time to retire this venerable interior, the EC removed the interior and replaced it with a Square D QO style. The can for the Frank Adam was huge (compared to that required for a QO) so the only real modifications needed were to remove the FA door on the cover, mount the QO door over this existing cover (with no extra openings, actually a very good fit), and then install the QO interior in the proper place with some type of standoffs to bring the circuit breakers up to the usual position behind the cover. It turned out to be a much less traumatic event for the wires inside, with no conduit cutting and re-fitting needed, or extra J-boxes.
Going by the "letter of the law", I guess this would not be allowable, but does this type of thing happen anyway? With regard to safety, I would think that this is far safer than a fuse panel with an open socket or two, as was the case with the FA.
Mike (mamills)
[This message has been edited by mamills (edited 04-03-2006).]