I reached out to TK and changed:

TK 1856
BCN-IST
9:55 layover
TK 298
IST-SFO

Still K class (Business). Good news that that my long-haul will be on a 787-9, with even numbered windows seats for me and my traveling companion. -- I've heard nothing but good things about this product, and I'm also chuffed that I'll get a chance to try out the Turkish Business Lounge as well, so there's that!