ONF, since you're trying to sell it your best bet is to sell it as is and let the buyer find:
a 2x3 Graflex (to fit Graflex SLR) focusing panel or
a 2x3 Graflex (to fit Graflex SLR) film pack adapter and make it into a focusing panel or
a 2x3 Graphic back (spring back to fit a 2x3 Graphic) and swap it with the Graflok back now on the camera.
Finding a 2x3 Graflex focusing panel or FPA will take longer than you have, finding a spring back and doing a swap yourself may cost you more than the complete and usable camera will bring.
Sell it as is for what it will bring and get out from under.