SS 100 hood/bonnet

It is my understanding that 3.5 liter 100s have wider radiators than the 25 liter. Is this correct and is there a measure or other means to determie which engine size engine size a bonnet was made for? Also any tips on determining whether a bonnet is original or not would be appreciated.

On an SS100 the bonnets are the same width, As for determining whether its an original , look for a few cra ck at the edge of louvres and places where the alloy has worn,
Additionally they were originally made from a gauge of aluminium no longer made , I’d have to look it up. Most repros are thinner gaige, because that’s what you get and it’s easier to work.
Post a picture if you have doubts.