KSA992 FBTA are the same gain as the FBU just come in cut tape not bulk. KSA1220AYS is fine and is the highest gain version for this part. . You may have to get the KSC1845's form Digikey or Element 14. The datasheets for each will tell you their gain values etc. I usually always use these fairchild transistors but when l have ran out etc l have substituted for BC's etc but the KSA992's and KSC1845's have better gains and have better leg orientation, usually you just have to reverse them to the originals.