Africa Tech Rep - got it in one. They are trying (understandably) to define all principal differences between their present fleet and "our" aircraft in order, no doubt, to hit us over the head when talking price. You are also correct that, had we had access to the Detail Spec, we could have got the answers but the aircraft and docs aren't accessible by us on a daily basis and the owner's tech rep is snowed under. The aircraft are PND/ND by the way.
XetroV is quite right too but the trouble is the price Boeing charges for even relatively minor upgrades - let alone, say, paper increases in MTOW!