Radiator upgrade experiences?

No. Have not

I also have 400/430 hp by the ET, And run a decrepit old stock rad from a 1973 Swinger 318 that had A/C; so it's a 26incher..... but it's in a 22" core-hole. It's so decrepit, it has patches on it's patches.
Nickel-plated naked headers and Painted Edelbrocks.

I run it at 205 to 207*F, on purpose.