I have a 1977 firebird that has a 455 in it. I was told that the motor was original but i cant seem to be able to find any info on it. Can anyone help?

 

Pontiac did not produce the 455 in 77 the last year was a 75 or 76 And I thinkl they only came in firebirds in early 70s and trans ams until 76. Find the date code behind the distributer and letter code on block to find what it came out of.