I have to agree with the others, Alloy is the way to go!
I always wanted to do it on the Sammio but i wasn't brave enough at the time and i regretted not doing it, so i'm so glad i used it on the Miglia.
I don't claim that my end result is anywhere near perfect, especially when compared to some of the other superb builds on here, but i love how it turned out.
I found that you can get very pleasing results quite easily and given the 'type' of car we have, any mistakes simply add to the look!
A few things to consider based on my experiences.
1) While you can buy Alloy sheet from B&Q they are very expensive and so I ordered my sheet from
https://www.metals4u.co.uk/
An additional benefit being that the packing they use can also come in very handy as well
2) You'll be amazed how many pop rivets you need
3) 1mm cutting discs on an angle grinder are great for chopping up big sheet, just wear goggles!
Good luck with whatever you choose, I'm sure it'll look great