If the elevator linkage were in a different spot, it would be pretty easy. You really need to move it anyhow. The control horn is near the trailing edge of the elevator. That isn't the best place geometry-wise. The holes in the horn should line up with the leading edge of the elevator. since this needs to be corrected, just make the pushrod exit on the side of the fuselage rather than in the center. Then you can run some sort of tiller from the tail wheel, through the horizontal stabilizer and attach it to the rudder.

Why do you want to convert it to a tail dragger? It may just end up being a ground looping handful. Then again it may not. Nothing wrong with tail draggers of course but I figure it's best leave well enough alone. Save the tail wheels for planes meant to be that way. Then again, messing with stuff just for the sake of doing it is kind of fun too.