I just fitted a new Nissens radiator in my LPT with AC. Relatively cheap and replacing is very easy. I would not mind doing it again if it would fail a little bit earlier than an OEM one. It could even be that Nissens is the OEM manufacturer as well. The fully aluminium ones from do88 are really beautiful, but a bit overdone for my 22 year old runner.
Regarding the capacity, I think the radiators for AC/turbo cars have the largest cooling capacity. They seem to have the biggest core surface as well (590x500 vs 450x418 mm), which makes sense as the condensor and the aftercooler are in front of the radiator warming up the cooling air before it passes through the radiator. The air passing through a non-turbo/non-AC radiator is relatively colder and the core area can therefore be smaller.
If you are looking to increase your cooling capacity, I would try to find out if you can make an AC/turbo radiator fit. The fan shroud is probably different for a start. But why should you want to increase the capacity? It has been sufficient for the last 25 years or are you preparing for global warming?
Rob