Steel is Real.
Phenomenal contribution to the thread!
On topic, I have a first generation Aqualu aluminum tub on my FJ40. I hated it when it was a driver but now that I primarily use it on trail only and it has been flopped a couple of times, I don't mind.
I think that you should stick with the fiberglass unless it gives you issues. It would cost so much to go back to steel and the advantages don't make the task worthwhile.
Have you considered contacting the former owner and asking him/ her?