[Salestax]

220 is the point at which most PCM's command the cooling fans to come on, then they shut off again in the 208 range. Heavy duty or SC radiators are probably an option and dont require any additional space, but not necessarily installed from the factory.
A more efficient cooling system will increase engine life and transmission life (as this is cooled as well), but if you're sitting still at 220 and not exceeding 240, you can either:

1) wait until a plastic tank fails and replace it with the biggest option available
2) replace it now with a single core OE part
3) talk to a local radiator supplier and see if a 2 row is available

If it helps, my 3800 Normally Aspirated has a 2 row.