Leaf Spring Selection

I run a used set of Mancini Racing Springs I picked up locally. Firm ride and work great at the track. 3/8" lowering block installed, 255/60/15.
Mancini Racing Extra Heavy Duty Leaf Spring Set

I can't figure out what those springs are...

Mopar A body XHD springs are #4510269 and 0268

Mancini's a body XHD are 1981 and 1982? And they are almost half price. 400 vs. 232