I have to say I don't think there was much difference each side, but I could be wrong in details. Dunno about roof.
If you can get to the NRM in York, check out the John Click photo collection which show blow-by-blow photos of construction details. Every rivet is covered. Click was one of Oliver Bullied's sidekicks.
Bullied was apparently an odd, and not very likeable person. When Inchicore technicians, drivers and staff engaged in building it pointed out various design difficulties, Bullied didn't want to know. "Well, FIX it!" was his standard reply as he walked off......