How to get into the trunk of a 65 Barracuda????

This is an unusual question but may help others.
In the case of the similar 73-76 Duster/Dart Sport models with fold down rear seat, there is a pair of vertical slide latches accessible from the trunk side. These are similar to a residential door handle/latch. Maybe you can slide a screwdriver against the latch from the the interior side and get it to slide open. Maybe have a friend next to you to pry the other latch? (Someone who is small enough to lay beside you)