Finally got to a point where I had hammered down enough bugs and recent feedback to draw and add in a different set of googly eyes. The technical part turned out to be not as bad as I expected, just drawing the different frames for them took time.

In Game Maker Studio, I add them in the draw event as their own sprite with a similar image_index to the car. They're designed for the player trucks, but I was able to scale them down for enemy cars to see if that will work and save time. So far, it's close but not perfect - I may be able to tweak the placement more or using masking.

Also, I'll find out soon if the red flash is ok or I should be using a white flash when a car is harpooned! Latest build attached.