Re: 514 AC Socket
An IEC would definitely need an adaptor plate. The less common type with mounting holes above and below rather than out to the sides might be a better fit.
The other type I've used (again this betrays my background in broadcast kit) is XLR-LNE. I think this type was only used in the UK, by the BBC and ITV companies. They are no longer made and go for too much money secondhand. Inevtiably I have a stock of them:)