I am using a standard radiator and an electric fan fron a scrap yard, Vauxhall I think. Cost ?10. I mounted it under the original bracket and it lines up with the cowl on the radiator perfectly. It has a rim on the outside of the blades that is about an inch smaller than the hole in the cowl.
Looks like it was made for the job and I have never suffered from overheating since.
A lesson I learnt whilst owning an Alvis TD21 was not to overfill the header tank, leave enough room for the water to expand. If you dont it will blow out of the cap, water level goes down, engine gets hotter, blows more water out...... a vicious circle.
Steve