The yellow spoiler is most likely a Lamborghini thing. Countach spoilers are typically the body colour.
I like the option of making the car a stock LP500S - it looks good, and having Sunstreaker displayed this way next to Sideswipe emphasises their 'twin' nature, even if he never appeared this way in the cartoon.
The
TFW2005 article has a fifth picture that shows Sunstreaker's pistol stowed in his leg.
Lamborghini supposedly not wanting the bonnet to split strikes me as kind of odd - was that really speculated as a reason for the delay in giving Sunstreaker the Masterpiece treatment? Takara could easily engineer the bonnet to be asymmetrical so that the Lamborghini badge isn't split if that was what they were concerned about. I think that having the middle of the bonnet separate from the sides and fold away in this instance probably helps to prevent Sunstreaker having comically wide feet.