The tensioner replaces the camshaft thrust plate. Bolts on using the same holes. It's a thrust plate and tensioner assy. I just added one to my truck ('96 Dakota) 3.9L to cure the dreaded chain rattle at idle (also replaced the chain and gears obviously)
Mopar didn't put any kind of tensioner on until 1997 and then it was only on the 3.9L (I think). However, it retro fits.
So,,,,,,,,,,,,,,seeing as the Magnum engines are basically the same (short block wise) as LA engines, it should work on those as well. One thing, with the tensioner it's a B*TCH getting the chain and cam gear on, lol!
Tensioner looks like the pic. It's Cloyes brand and pretty sure I got it from Rock Auto.