Torque converter issues

I have a Murray explorer that came with a predator 420 mounted with comet torque converter, no plate. I’ve got to remove the engine to replace the piston and rings, in the meantime I want to mount my predator 212. So, I’ve installed a 30 series driver on my 212. But the rear secondary mounted on the kart is an older 20 series. What do I need to do, to get these to work properly? Am I gonna need to replace the secondary to match the 30 series driver? Because I’ve looked at the 20 series, they are expensive and hard to find. Can someone help me out here?