I've been trying to do a headswap for weeks now, but I just can't get the transition to work well, because the body has 26 vertices at the neck while the head has 34.

I tried various diamond patterns in the topology to either make both 26 or 34 vertices, but it always ends up making the shading look messed up.
The body's also very well-made, I'm scared to mess with the topology too much.

How do I do I do this headswap?