This would be better answered down in the IH forum rather than the implement forum.
As far as the pits. How much are you going to be using the tractor?? I have had several tractors over the years with pits in the bore. All that will happen is that the pits will hold some oil and so the tractor will burn a little oil. IF the pits are real high in the bore they will not use much at all. Just run a little hotter spark plug and it would be fine under the low houred usage most would be doing with an F-12.
As far as what sleeve will fit. That you need to asked some of the knowledgeable IH guys on the IH forum. They are a pretty friendly bunch down there.