The 351C. Struck more fear into more BBC owners than about anything.
And oh what a sound.
When I had mine (70 Cougar) ,, it was in ‘79 to about 82 ,, I didn’t run into many “RAT” powered cars but the Buick GN’s were out in force in my area... the early cars were no problem unless they were worked on.. my friends dad had a 440 Superbird that spilled it’s crank and rods out on the highway ... it was in 4th deep in the big end of the tach..