If you know the guage steel (or aluminum, but I assume its steel by the weight) used in your stock tank, you can compare its strength, to the impact resistance, and bursting strength etc… of the Crosslink polyethylene.
I’ll look around a bit more to see if I can come up with anything else…
EDIT:
I found a few tanks made of 16 guage steel…
I found a few Polyethylene tanks With a wall thickness of 1/2". However, I’m not sure if they’re LINEAR, or CROSSLINK.