As far as im aware, The J15 is just a stroked J13. I haven't seen many 620s here, and most that came here were only cab and chassis. So unfortunately most 620s have flat decks, like mine did. I managed to source what I was told as a 620 Bed but it actually is a 720 bed. Bit of a pain that the lights are different but no biggie. Still weighing up if I use the 720 lights or modify the back to fit my 620 lights.