75 360 duster

What's the difference between the j360 and the L 360? My vin is a L Just wondering what makes it high performance
J - 360 1 - 4BBL 8 cylinder "LA" engine

K - 360 1 - 2BBL 8 cylinder "LA" engine

L - 360 1 - 4BBL 8 cylinder "LA" engine (high performance)