Thankyou vekia , i tried your solution , Its working
But a small problem , at the time of module installation me getting one error " Unable to install override: directory " , i think its becouse of existing root/override/classes/product.php , right ? , If i deleted this product.php then my module installed succesfully, any other way to do this without delete product.php from root/override/classes/product.php ?
Thanks