What are the best visa options for staying in Thailand for 8 months from the U.S. given that METV and STR are not available?

I think what you mean is you WANT to come here and stay for 8 months. ;)

There is no visa option that lets you do that which you can buy at a thai consulate before you come in.

Your best bet would be to get a single entry tourist visa from the consulate in your country before you come here. When arrive you'll get stamped in for 60 days and you can extend that once for 30 more days at the immigration office here.

I'd say do that and during the 90 days you will be able to stay here LOOK for longer term visa options