Larry at Triple M Plastics in W. Kennebunk (800) 873-7767 or (207) 985-8012 about a 3/8" poly tank.

And Bud at Luther's Welding in Bristol, RI (401) 253-5550 about a 1/8" alum tank.

Get their opinions and decide which you want, I found these guys to be very good at what they do.

POLY > probably will never fail; more expensive, maybe even twice as much; translucent; more baffles required (and then perhaps more access for clean-outs, although Larry says you never have to clean ? because diesel doesn't stick to the plastic), will probably weigh more.

Cheers, John