If someone is serious about doing smaller acreages (by today's standards)... then I think they could get along OK with something like an old Deere 4400 or 6600 or even 20 series of those machine... or an old IH 1460. All of those were decent machines, rebuildable and fairly reliable when you do rebuild them.
If someone wants to go farther back in time then that... I think that's best classified as someone looking for an amusement.
I ran an IH 615 for several years... and it was a constant battle trying to keep ahead of repairs and dealing with stupid little problems never mind trying to keep gas in the tank. Then go trying to make the parts you could no longer buy... constantly devising solutions to problems that the parts department had no answers for.
Quite honestly... if I was buying a machine today it would be new enough to have a turret unloading auger so it can at least unload into a truck without digging a hole in every field. Most of the problems I had with the 615 were in some way related to either the head or the unloading auger...