Cooling problems are a pet pieve of mine and living in Phx. Az. makes for lots of pieve. As a builder here is my 2 cents, I know there are many ways to skin a cat but this works for me.
If car only overheats in traffic then overall system size is ok with air flow being the issue. You will probably need to tweek system as well as air flow as you may not be able to get enough airflow due to space limits. If it just runs away period then many problems are possible. Many people overlook
oil temp as an added heat source so I use
oil coolers with sucker fan if possible. I always use a T-stat on
oil cooler as you need to maintain at least 200 to outgas contaminates in oil. Then I run a 180 coolant T-stat so system has time to cycle. I like Ron Davis's aluminum rad. but biggest is always best. Use the biggest CFM puller fans possible with shrouds. Aftermarket waterpumps also have better flow than Checker rebuilds! Be careful with RPM reducing pulley on water pump also. I like pusher fans in addition to puller fans. The bit about them blocking airflow when not turned on is bull - they just freewheel from airflow if at speed and direct airflow into rad. I use 15 to 18 pound caps with expansion tanks if possible and check system design for air pockets or reduced coolant flow.
On the tough ones I modify flow by taking coolant from top rear of engine (drill and tap manifold or build nipple into softplug) and route to just under T-stat so increased flow from rear of engine but behind T-stat increases flow volume from hottest part of engine. I also run 2nd remote cooler with fan under car on the impossible cars. There are more little things to do but I am running a 542 inch motor in Phx. at 180 and no more than 200 in traffic. But it is a dry heat on a warm day of about 118 in the shade!!!
