According to the service manual, the bonnet must be removed on a Series 2 before the radiator can be removed. My 1970 Series 2 Coupe has air conditioning. Must I remove the bonnet or can the radiator be pulled without removing the bonnet?
Yup, I have done that on my SII. It just take patience. In my view the biggest issue is reconnecting the bottom hose after replacing the radiator. Once out you have the choice of a new aluminum rad or have the old core replaced with a new higher efficiency core (my choice - and it does fine in the Dallas heat). I recommend a new cooling fan system for a hot summer climate especially for city driving but that may not work for concours championship cars. I also suggest wiring the cooling fans to a hot circuit (rather than thru the ignition so the fans run until the engine has cooled after you shut down the engine (as in modern cars). The down side is a flat battery if the Otter Switch fails in the on position but I bet there's someone out there who knows how to install a timer on the circuit.
If during the process of radiator removal you are tempted to release the mechanism limiting the bonnet travel, (risky at best) be certain to also release the rod that controls the front license plate tilt. Failure to do so will result in at least a bent control rod. Been there, done that. :-) It's easy to overlook as it's almost hidden down there.