Once again, thank you gents!

...only one gem in the pic, hope it's not lost already! 
No worries; the other one is still safely attached to the aforementioned card; I only took this one off to fit it. Once I do the other light, I will put this gem back, as I will only be attaching them permanently after painting.
There are also two larger ones and a really large one of the card, so I might eventually use one of those for a searchlight maybe?
...How did you bend the pipes?
Well, for starters; they're not really pipes, but rather, they're made from rod. And I simply bent them slowly by hand, sometimes using the handle of a brush to curve it around. Do it too fast, and they'll crack, but done with a bit of patience, you can even re-bend and correct at leasure.
That alone makes that I'm (still) confident I can replicate the first set.
Bertrand, you make a good point, however, I'm going to try and replicate the pipework first. Only if I find it is really impossible to make a (good approximating) mirror set, will I consider that.
I had already thought about it and had an idea of having pipes run over the bonnet from right to left, attaching to the existing pipes. But that's only when I'm not able to make it symmetrical.
Coincidentally, the model kit I'm basing this on is also asymmetrical. It has two doors on the left and just one on the right, with a large radio set where the door should be. Also, another limo conversion on the web that I have been drawing inspiration from, has a cilindrical gun turret/tower on the right hand side, which could be a good backup idea. I do plan on an MG on the roof, be in it a turret or pintle mounted, so making it offset from the center is always an option.