I have owned a 70 Barracuda 383 and a 67 Dodge R/T 440. Talk about design flaws! Crappy brakes, unibodies, very rust prone and crappy transmissions. I can't even watch "Graveyard cars" anymore because if I hear him say "Mopar or no car one more time... lol. Like mentioned every engine has "flaws" I have rebuilt most of them. Buick 455 needs the oil pump mod if you want it to live. If Pontiac had a design flaw it was those cast rods. Put a Chevy guy behind the wheel and pop goes the rods.
Ever see the oil pump drive in an Ford "FE" engine? 1/4" shaft. Had one snap when the nylon timing gear managed to get a piece into the oil pump. I do like those Engine master vids on youtube. Very informative.