On a 175, I'd get it as level as possible. It's a lot of weight!! Is your lean full or empty? I'm pretty sure if that lean is empty, it will increase when the tank is full. Another concern is if this tank is on a concrete slab ( aka basement) or supported by house floor joists. If this is on joists, I highly recommend you level to almost perfect and confirm you are perpendicular to the joists and not parallel. Even then, I'd give thought to additional floor support.
Edit for afterthought
