When Martin started their Canberra/B57 programme, the reason that a "sample" Canberra had to be used to "get the drawings and things" right was that English Electric naturally worked to British Standards (BS) right down to the sheet metal thicknesses, nuts, bolts and such while, again naturally, Martin worked to US Standards. Conversion to US Standards was therefore a normal part of the task...
That's perfectly reasonable. However, it's hard to believe that they needed an entire aircraft in order to achieve it. Surely, if the drawings were comprehensive enough, even in preCAD days, they could have been converted? Perhaps you can clarify, my understanding was that they were all redrawn from scratch.