Thanks for all the input guys. I'm thinking hard about a box stock build, because at contests it's one of theose catagories I've never got an entry for. I hate yellow, so was leaning towards Inca Gold. Which should look groovy with the red tinted glass. However from what I've seen the engine does look really out of scale - too small. However if I'm going to change the engine, I'll likely start replacing all the other lil things that bother me, like those funky front seats, so again I'm leaning more towards a box stock build.
Was this based upon a real car? A Google search has revealed only the kit, some die-casts and the like.