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The only LEDs you could put on the outside that'll make it stand out are:

1) The cheap LED bulbs in place of incandescents which every kid does to their car right away.
2) Under lighting which every 10th kid does.
3) OR converting to LED lighting and doing it well (I can think of about 5 people total who've done it on a MKIII and it's never easy... expense varies depending on resourcefulness).

Personally, I recommend you not wasting time on any mods until everything else is in excellent shape. Spend that time and energy flushing the coolant system thoroughly, replace transmission and differential fluids, replace shifter seat and bushing (if manual). Convert to fluidic windshield washers (the ones you find mounted to the wiper arm on Buicks and Cadillacs are nice, then you can delete the hood nipples. Replace the tiny driver's side footwell light bulb with LED light bars in both footwells. Do the same for the trunk light. Replace all vacuum hoses and test all VSVs. Get every little piece of maintenance done.

The easiest way to make sure you stand out with a MKIII is to make sure it's not always just standing there (broken down).

Their looks aren't so exotic that they aren't always confused for half a dozen other (lesser) vehicles... so forget about making a big splash with just some different bulbs which no one is going to notice anyway (unless you hang out in dark parking garages).

Of course there's always spray paint or roller paintjobs. :P