I think I understand your question now. If you use want to express a hypothetical situation in the present, you would use past subjunctive.
"They are acting as if it were the nineteenth century."
"What if Napoleon had won at Waterloo?"
In the past you have a few options.
1. Past subjunctive
"They acted as if it were the nineteenth century."
"What if Napoleon won at Waterloo?"
2. Pluperfect subjunctive
"They acted as if it had been the nineteenth century."
"What if Napoleon had won at Waterloo?"
3. Past subjunctive + perfect infinitive
"They acted as if it were to have been the nineteenth century."
"What if Napoleon were to have won at Waterloo?"
The use of these depends on a variety of facters including what you want to express and the length of the action (continuous or instantaneous). However, for the 19th Century sentence, you should use the first. For the Napolean sentence, you could use either the for or second, though I would use use the second to avoid wordiness.
Hope this helps.