Looks to me the only difference in the radiators is the filler neck. Anyone do this swap?

 

Only every 90 and lower jeep owner.... Been done thousands of times

 

There's a little more to it (the conversion) than just the radiator/filler neck. Closed system (old) uses a pressurized bottle/cap, open system (new) uses a vented bottle that must fill/empty from the bottom and 2 totally different caps (on the bottle).

 

That is obvious pressurized tank versus overflow tank, just wanted to know how it fit and worked And why the after market 3 rows all seem to be for the remix

 

Well,.......from the way your original post was written, it wasn't obvious to me, or maybe others, that u knew the bottles, and how they functioned, were different.

I can't imagine there being any COOLING advantages, open vs closed. The rad cores, water pumps, fan clutches and t-stats are the same on both system types. Only drawback to the closed system is the cap-to-bottle seal as the plastic ages.