If you've got good flow through the radiator, it's not full of crap in the cooling fins, and it isn't leaking, then your radiator should be fine (...it's a radiator, not a missile guidance system). If it's only heating up when your sitting stationary (or close to it) in traffic, put a shroud on it and move on. Your problem will go away.
The guys who are saying they get along fine in 100+ weather sitting at idle with all accessories going most likely have multiple core radiators that are doing a better job at cooling. I have a '74 F250 with a 390 and no shroud that does just fine; however the four banger in my YJ just won't tolerate it. After I did my CJ front clip swap I ran without a shroud until I got around to putting my e-fan in. It acted just like what you're describing now. Temps were fine until the weather was hot and I was sitting in a drive through or in heavy traffic.
“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.” ― Robert M. Pirsig, Zen And The Art Of Motorcycle Maintenance: An Inquiry Into Values