In bed fuel transfer tank question

Looking to ad a 35-75 gallon in bed fuel transfer tank.(not an auxiliary/plumbed in) What type should I get, aluminum, steel or poly? Aluminum scares be because it is so thin, and steel will rust.

I bought my steel tank to go in a new 1983 truck. The tank is now on it's third truck and doing fine. Next year will be 40 years on the tank.

Bill