years and motors-need help for emissions rules

[RustMaster87]

If I have a truck that has a 1980 title, what can I run for a motor in the state of NH? Do I have to run a motor that is specific to 1980 or newer, or could I use a motor that is custom built? Could I use the same motor in my truck as I would in somthing along the lines of a Chevelle or Camaro? I have a possible find on a real nice motor from a friends car that he is parting out and just want to make sure it is legal to put it in my truck.