Thanks guys.
I definitely understand the purist side of things. I'm also a customizer of the numerous vehicles I own.
The difference in what I do is that anything I build is easily reversible and utilizes original mounts.
For instance, one of the vehicles I own is a 67 Humber Super Snipe. I'm about to install a Jaguar rear end using a custom engineered (pain in the Ass) sub frame mount it, rather than just weld it or mounts in. I've also got a Jag front end which I'll modify to suit the Humber mounting points.
The Cox and Greenfield are done the same way. Whilst the drive and body are far from OEM, it can all be reversed if the need arises without any sign that funny business has occurred. No additional holes or tabs have been drilled/welded.