Weren't they originally built with cast iron tankage? That's an upgrade I would anticipate making if it hasn't been done.
Though I could be mis-remembering from another manufacturer.
I got an Old Fat Boat
She's Slow But Handsome
Hard In The Chine, but Soft In The Transom
I Love Her Well, And She Must Love Me
But I think It's Only For My Money
. ..... Gordon Bok