What you did with the paint on the body work looks good. The uneven paint and mixed colours suggests cracking and and the top coat letting go before the primer. Without a full on explosion of the fuel in the tank and a full burn most of the combustible material is probably going to be in the passenger compartment and the wreck will burn until that "fuel" is expended. the areas nearest are going to take the worst beating from the heat, particularly the roof. I've seen heat distortion done to tires by just shaving the lower part of them down to suggest them flattened and sagging.