You can use your carb tank, "all" you need to do is locate an AE86 pump carrier and it will bolt straight into the top of your carb tank in place of the carb pickup that is there now. I will however admit that AE86 pump carriers are a little hard to locate.
The carb tank only differs in that it doesn't have baffles around the intank pump pickup.
I am not aware of any other tanks bolting straight in, with fuel inlets and so forth in the correct position.
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