A spare tire on the hood only really works on a LR Series for two reasons:
(1) the bottom of the windshield is a far amount above the flat hood surface (due to the vents at the windshield base).
(2) old skinny tires didn't stick up that high. I won't put a spare on the hood of a Defender unless I was running skinny tires. A fat tire blocks a bit much view:
Compare that to a Series 1 with a skinny tire that in no way blocks your view:
Also realize those old Series Rovers generally weren't traveling fast enough that the tire on the hood screwing up aerodynamics matter. The amount of wind noise that it would generate on the hood of modern truck at highway speeds would be bad.