Actually INR fare ban on non-residents has been eliminated, but web sites have been slow to change and even employees slow to learn. So, by all means, buy only INR fare.
I just don't want to buy the ticket, show up and tell me that I was ineligible to fly on the ticket with my US passport...
This won't happen. Even in the bad old days, the worst that ever happened was they asked you to pay the difference.
A practical problem you may face is that many Indian carriers and travel portals are banning online/phone use of foreign-issued credit cards (in person is ok). I don't know about go-air specifically.
If you have trouble buying the ticket, let us know. There are ways around it, less convenient but better than paying predatory USD fares.