6bolt has thicker rods, can handle more stress.
It Isnt prone to crank walk like the 7bolt....
Has different sized head ports and bigger intake manifold/ tb.
6bolt came on 89-92 1g Dsms. 7bolt stated late yr 92 up.
Rod knock has nothing to do with engine design or build... Rod knock means
the engine is damaged due to poor octane/fuel/ poor tune, leading to detonation
or from running improper oils/ or from not having any oil at all and running the engine dry or with low oil pressure...