I run 6" H-beam rods with a Scat forged one-piece crank twisted by forged +0.030" Wiseco flat tops in my 87 355. There is a slight torque advantage coupled with a slight decrease in piston side thrust - essentially, less energy is wasted and more energy is transferred directly to the crank. The engine consumes ~1 quart in 3,000 miles, which may be related more to short trip driving. You may need to relieve the base of the cylinders for adequate rod clearance. Although I'm a proponent of 6" rods, in reality, benefits likely will go unnoticed in a DD.
My only regret is that I didn't clearance the block for a 3.75" stroker and groove the leading sides of the lifter bores for enhanced lobe oiling while I had it apart.