I ran a Champion 26" 3 core (CC374) in my Duster for over 12 years. I run an iron headed 340 that's .060" over and is probably in the low 400 hp range. I never had any overheating issues with it, even driving it on 110° degree days in traffic. Most of that time was with a '95-2000 Ford Contour dual fan set up. The radiator did finally start leaking from the fin to tank junctions, but again, 12+ years and close to 50k miles in that time. I think I paid around $200 for the radiator so that's a pretty good run.
I had to drill a couple of new mounting holes in the flanges of the radiator, but considering the price is half what others are, and not even all the "direct fit" radiators actually fit either, I think that's a VERY minor concern.
Core thickness won't be quite as much of a concern on an E-body, the clearance is a little bit better. Not by a huge amount or anything but not as critical as an A body. Technically the CC374 was an E-body small block application. Currently I'm running a 26" 3 core KKS radiator, similar price point as the Champion and the same part number, it's a KKS374. The KKS374 dimensions are slightly different from the older CC374 Champion, but close enough not to cause any issues. Again, drill the upper two mounting holes in the KKS flanges and away you go.