Carpet and my humps?

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So I am ordering new carpet for my 1972 Chevy truck and I am confused on how to pick the correct carpet kit for my humps.

I have a 1972 chevy truck with a turbo 400 (all factory original).

Some carpet vendors only specify low hump or high hump, others specify low hump, turbo 400 hump and high hump.

So I know I do not have the high hump, but what is the difference between the low hump and the turbo 400 hump?

Thanks