There is no Form 1040A now. Tax reform has changed it all, and everyone gets a Form 1040 with six possible schedules for various data entries.
If you receive SS and a small pension, you might not even need to file a tax return.
DO I NEED TO FILE A TAX RETURN?
https://www.irs.gov/help/ita/do-i-need-to-file-a-tax-return
Who has to file?
http://www.irs.gov/uac/Do-I-Need-to-File-a-Tax-Return%3F