I am new to Team Buick and have a question you have probably covered a thousand times. I will ask anyway. I have 72 GS 455 convertible. Motor code stamped "F 442" at the deck near the oil dipstick. Front of the block near the timing chain cover is 43X168---. Can anyone tell me what I have? I have had the car almost thirty years and was told when I bought it that it had a warranty replacement block. I assumed that was crap but lately have been wondering. Any thoughts?