How can i get a title????

Sooo heres the story. I bought a 72 duster rolling body when i was 16. It didnt have a title. i was young and dumb. The body is one of the most solid cars i've seen. I got all excited so i bought it thinkin i'll get a title for it somehow. Well long story short life took over and i could never research or find out how to get a title for the car. I would love to get a title for the car especially since someone has offered me a straight up trade for it if i can get a title. Does anyone know how i could go about getting the title and btw its a New Jersey car. I live in pa. THanks any info would be greatly appreciated!!!!