If you use your car only in summer like mine the first (and the cheapest)thing I did when my engine overheat was to run my engine fill with distilled water and Waterwetter, try this and you will be surprise with the temp. drop...
Antifreeze have not the best heat transfer properties.

Mopar viscous fan and shroud must be add to have the best cooling, check timing If you can use direct port vacuum on your distributor it will be better.

I have a 451 c.i.with 11.25 c.r. and a small 22 in. rad. never had problem even in big traffic jam at 90F.

No, it gets warmer if sitting still for a long period..

& that is even worse than stop and go cuz the pump (water flow) and fan (air flow) speeds are the slowest they can possibly be plus not even a hint of air being forced in cuz of no forward vehicle movement

being in the radiator business for 35 yrs i can tell you that its possible to expand a bottom tank from 2inch to 2 3/4 inch,any good rad shop should know how to do it

That's one of the main reasons I went with the Monster fan. Controller picks up the fan speed as needed without adding more fuel to the fire.