The 560 exhaust doesn't bother me much. I'm planning on making some headers for out of some of the old ones I have from other projects. I'm sure I can cut and weld something.

K jet will be tons-o-fun but as far as I understand it the D jet isn't something I can tune to work on a 560 and I would hate to put a carb on it when I have access to (primitive) fuel injection.

As far as the Pontiac goes Mike, I like the torque and the blocks are both "middle weights". The Pontiacs also have monster 3.25" mains.