Hello Andu ...
I play guitar and organ, although I'm not all that good on either! I play acoustic and electric guitar, having 9 altogether, including two Strats, a Gibson Les Paul, a Paul Reed Smith and a 1928 genuine Dobro resonator!
However, to get back to the subject of your post, why not try Pachebel's Canon in D major (often played in C major). Then the organ can play a continuo when the guitar takes the solo, and the guitar can arpegiate an accompaniment when the organ takes the lead. The other thing about that tune is that the guitar can play clean distortion-free for some of the variations, but can play up high with lots of distortion, chorus and delay for the main theme.
I hope that helps!
Ken.