Tried fitting the new radiator and discovered it was a bit thicker than the original (maybe 10mm) so wouldn’t fit. Cut a few bits out of the chassis to make it fit.
After that I assembled the front end of the car and installed the bonnet to ensure the radiator didn’t hit the bonnet. Unfortunately the new radiator is slightly taller than the original so it now hits the bonnet. Tomorrow I have to have another go at the front sub frame to make it fit.