Well, I consider a/c that carry pax and cargo on the same deck as Combi or "M". Of course sometimes this may be achieved due to them being QC models.
As for the specific types/airlines I mentioned:
I´m not sure whether the a/c AS referred to as "737-200 Combi" were QC or not.
I´m not sure whether the RAF L10s´ configurations are changeable or fixed.
Four of the GAF´s seven A310s are MRT, i.e. Multi Role Transport - they have a SCD and can be converted from all pax to cargo/pax to MedEvac/pax configuration; so I guess you could call them QC if you wanted to. Their 707 were the same too, btw (except for the MedEvac).
And you´re right about RV´s Electras. They were indeed "LOM"s.
And what about this 727-100 operator in Northern Canada, Bradley First Air or something - didn´t they have 721M as well?