EDO 1650's are approved. See: http://www.airweb.faa.gov/Regulatory_an ... enDocument
And, by the way, the FAA Library site has information on every Type Certificate and every Supplemental Type Certificate issued.
So, if you need this sort of information, search that site for the make and model aircraft. Search first under the Type Certificate, since it could be approved there, by the manufacturer.
Then search for STC's for that make/model aircraft.
It's easy, give it a shot.