what is the etiquette for writing to people in the past? Should I avoid mention of any deceased mutual friends or relatives, be truthful but only when asked explicitly, or should I just flat out lie for my own amusement?

Currently everyone I write to who lives in the seventies believes the Falklands war escalated into a global conflict, and that we struggle to rebuilt civilisation in the countryside while gangs of mutants fight amid the ruined cities.