IH published a Preventive Maintenance Manual back in the 1950s when the 140 first came out. I am not aware of later versions of that manual intended for a very late 140s like yours. Probably 90% of that manual would apply to your tractor (main exception - electrical). However, I suspect the information you are looking for is in the Operator's Manual. The Operator's Manuals were updated several times. I think the later editions included everything that had been in the Preventive Maintenance Manual. You probably want the latest edition to match up with a 1978 tractor.
By the way, the manual server on this site has very little that is specific to the 140. Of the manuals I mentioned here, the Preventive Maintenance Manual is the only one available. Binder Books, as previously suggested, has good reprints of manuals. They have several versions of the 140 Operator's Manual.