Big block duster pain in the A$$

Fisher said
I did the oil pump mod on my 6 K frame before hand. Even fit the K frame to the motor while it was on the engine stand to make sure it all fit before dropping it into the car.

Im dropping a 383 in A 73 duster with the shumacher mounts n s6 k, i have never heard of the oil pump mod can you explain what should be done? Thanx