Really tough for it to be American made at that price.
The only person associated with GN's that I know that could do this is Turbofabricator. He might be able to do it for less than $900 sumped etc, but I doubt for $500.
Ricks Hot Rod had a sale and it was $900 shipped with the baffled sump, stainless straps and sending unit.
Probe Turbofabricator, he might be the only one willing to get the program rolling for all the future E85 GN's.