I'm not sure what you are asking here.
However if you are using past tense narrative then all your narrative and dialogue tags should be in past tense.
Past tense narrative.
"I think we have time to discuss that other matter," he said, when they'd completed their work.
"I agree," she said, as she turned toward him.
Present tense narrative.
"I think we have time to discuss that other matter," he says as they complete their work.
"I agree," she says, as she turns toward him.
I can't think of any reason to...
"I think we have time to discuss that other matter," he says, when they'd completed their work.
"I agree," she says, as she turned toward him.
...do it this way. It would be incorrect.