It will work. As you know, the Kit specifies the 9800R->6R Edcor, with an 4 ohm load (your speaker impedance isn't fixed value) the tube sees a reflected impedance likely closer to 6500R. Reflected impedance make my brain hurt....

Ive built a couple versions with various rectifier options, using the 9800R >6R a 5000R>4 or 8R and a 6500R > 4 or 8ohms. My favoriate is the 6500R impedance, 4ohm tap, 8 ohm full range speaker, although the difference is slight on the 4ohm tap. On my o.g. zkit. with the recommended edcor in the basement now, I use RP600m, which are closer to 4 ohm, and they sound great. I read somewhere in this site that the new UFO transformers are 6.5k primary impedance into the 4/8 ohms.

You have an UL/screen tap on that transformer which should just be covered with a piece of heat shrink.. Or you could wire in on a switch off the  1k triode strap resistor.

Nonetheless you will make good music, it will work.