26" radiator for a slant six?

Silly that people think a 26" wide radiator won't cool better just because the opening is 22" wide. The air doesn't have to go in a straight path. More surface area will allow more cooling. You may not need one in France, unless in the south. The radiator in my 1969 Dart slant boiled over several times and it had I think a larger radiator since factory AC. That was in Georgia, which rarely gets >95 F, so >110 F in CA/AZ would be worse. But, the problem was usually coolant loss from a split in the seam in the front middle. That plagued the earlier round-top radiators (my 1965 Newport split there too), but I think wasn't an issue in the later square-top type you show.