Match the width of what you have.
Might aim for a "HD" or "Police" lining, if possible. Raybestos or similar OEM replacement brand. Chk Rock Auto for pricing, in general.
As for the cracks, the shoes on our '66 Newport had cracks in them, though not quite as intense as the pictured ones are. Being the frictions are bonded to the shoes, might never cause any problems with flaking off or similar. Looks like lots of good lining, though. They could last a good while longer as is, from what I've seen over the years. BUT they are not expensive. Your call.
CBODY67