You should NOT put the regular dacron filters in place of the Tri-X. It's a matter of flow - the Tri-X have sixty+ square feet of surface area, as opposed to the 30 square feet on the C-6430 (Watkins part No. 31489).
As soon as they get dirty, you will be giving the pump a real headache with cavitation, and you can do damage. You can use the 31489 on the Circ pump, so if you have four of the Tri-X you are in business...
HTH