Just got done finishing this beauty up for a Halloween parade for my daughter.
I used flexible blue electrical conduit for the side fuel hose. I was originally planning on blue vacuum hose from Lowes, but I just couldn't justify spending around $10 for the short amount I'd need. The conduit was only a few dollars. In total, I think I spent $30 on the whole project (thanks to finding a very old hand-me-down cozy coupe and having a bunch of spare junk on hand).
The decals and license plates are printed on weather-proof avery address labels left over from my proton pack. I used a bit of extra spray adhesive to help hold them on. Overall, they look great.
Due to size constraints, I had to combine and omit items from the roof rack. You can see I've got some PVC pipe, a bowl for my modified radar dish, an electrical box, and the light is made with a pencil case. I also got some blue reflectors for the front blue "lights".
Inside the pencil case are a pair of strobe lights (that didn't photograph very well) and three bright blue leds (that you can kind of see up towards the front of the case). At any rate, they are much brighter in person.
For sound, we're going to sit an ipod with an external speaker in the rear "trunk" area playing Ghostbusters theme covers and Ecto Siren effects.