Tarago spring should be the same. Lowering the car with coilover seems like a norm in Japan especially for this estima/tarago model.
I own 2008 estima so i undestand what you mean.
Replacing the suspension would be very costly.. i would suggest to consider first adjusting the coilover height to max and see if that gives enough clearance.
And if not enough, check tarago spec for the same year.