Installed you won't be able to tell. Pop open the right side panel and look at the two coolant lines coming from the tunnel cooler. If they look squished against the corner of the head than it's the older style. The updated tank provided a lot more room for the coolant lines. Again if it's the older style the fuel level sensor will be tight against the lower part of the steering gate(aluminum square tube), the updated one has room between the sensor and gate.
If it's off the sled it should be easy to tell because there will be an indentation where the coolant lines go. I would urge you to save and get the newer style, I've had both and the newer one fits a lot better.