Oh, so,
now you share that your 1968 /6 is in a 60-62 A-body? Might have been useful information before don't you think? Not that it matters. You still need to maintain the same engine temperatures, and you still don't necessarily need a $450 custom radiator. If you think that's the only solution, spend your money, doesn't hurt my feelings.
The whole thing is kinda interesting, because your car isn't running hot based on the information you've posted. You have an inaccurate aftermarket temp gauge and a poorly located sending unit, but that's about it. And now you think you need a new radiator for some reason? Not with a temp of 185*F with it idling in the driveway on a hot day you don't.
As far as the rest of it, 19" radiators were used for /6's in A-body's all the way up through 1974. Probably longer, I just don't have the part numbers handy. You can see all the sizes offered here
MyMopar.com - Radiator Specifications
Maybe you didn't know that on the later cars at least, a 22" radiator will bolt right in place of the 19" radiators. Same mounts and everything, straight bolt in. Now, it may not be quite that easy for the 60-62's, but if I can figure out how to put a 26" radiator behind a 22" radiator support you should be able to figure out how to install a 22" radiator in a 19" support. Both are 2 core radiators, the 22" will of course have more surface area, which means better cooling. There's more than enough room to mount the 22" radiator in that radiator support.
The pulley to radiator spacing is tight, but it's not the worst I've seen. You can still use a shroud. Maybe not a factory one, but even a fan shroud that would fit in there would improve your radiators efficiency. You're also still using a factory fan. There are mechanical fans out there that move more air than the factory design. But again, based on the information you've provided so far, you don't need one. Just a better aftermarket temp gauge and sender.
