Right. Maybe I'm not explaining it well.
The old module says there's some monsters and treasure in the room.
The referee has two choices:
1) Use what's written and try to make it work in a different system, i.e. mod things to work "good enough" in the new system, or; 2) Use the new system.
So why not just use ignore what the module says about the quantity of loot and instead go with what Shadowdark says? What level are the PCs or the module and roll on the appropriate Shadowdark treasure table instead of using what's in the module. Seems like that would be dramatically less work than trying to convert the loot from TSR-era D&D to Shadowdark. Same with monsters. The module says orcs, okay...so use the Shadowdark orc stats.