1991 Dakota 318 TBI Belt Tensioner made of Unobtainium

Well, looks like the tensioner is going out again.

I looked at swapping the Magnum stuff onto the from of the motor, but got tripped up with the missing bosses on the front of the LA heads.

Magnum Serpentine on a '91 TBI 318? Without changing the intake?

So I am going do the Gates #38139 swap.

If only I had gotten the 5.9 swap done this last fall.
That tensioner is just a spring, right? What's failing on it?