Well the first question is whether your rims are even tubeless compatible. If not I would end the discussion right there.

As far as setting up a a non tubeless rated tire tubeless… If the tires are wire beaded, what I have read indicates it is not worth trying. I’ve never tried it myself.

If they are folding bead…it usually works, but I would ask somewhere like MTBR if anyone knows much about the WTB stuff. I’ve successfully run many non-tubeless tires on Stans rims over the years. But to be on the safe side, I would put the new Tubeless Compatible one on the front, and do the non-tubeless rated one on the back.

Check to see how tight the bead sits on the “shelf” of the rim. If it seems pretty loose, I would skip doing a conversion. But if it is tight enough to be able to seat the bead with a floor pump, i’d call it good for the rear.