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I always hate being the source of bad news. But this particular unit has no conversion kits at all. After the Pulse was dropped during the C.O. issues, they tried to get as many as possible off the market by discontinuing many of the parts. There is only one way you would find these parts and that is ff there was a junk Pulse somewhere to recover the parts.
And even once you have gas valve and orifice, you need the membranes and diaphragm material for air/gas mis box.
I am very sorry, but if there were ever a furnace that was hard to get parts for, it is Lennox Pulse. Even ones still in use are supposed to have the heat exchangers checked every couple years with a special pressure test.
I realize you may have gotten good service and no issues from this unit style, but the parts are getting harder and harder to come by. You can get aftermarket gas valves, but not the natural gas orifice...The gas valve is around $300 for the aftermarket
The g24 will be the same..gas valve but no orifices