vec_for_vertex
vec_set
my.scale_x,y,z

first calculate 2 positions you want your spring to be attached using vec_for_vertex on car.

then vec_set your springs position to lower one.

usin vec_sub, calculate the vector that points from you one point to other. use vec_to_angle. this will give you the angles which you spring should use.

then using ve_length calculate the lenght of thet vector and scale you entity accordingly.