I got my tank from Trail Quest. It's a 22 gallon with a steel skid welded on. They also built it with the mounts 1" lower, so it rides 1" higher (I have a 1" body lift). They also built it for a GM in tank fuel pump to go with my EFI. It has a tapered rear, so it doesn't affect departure angles, and so far, I think I've only hit something with it once. The bottom with the skid is almost 3/8" thick (1/4" diamond plate skid + 12 gauge tank).
I really like it. www.trailquest.com
Bob
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