long rod motor
What are your plans for the motor? In 99.9% of applications, you would never know the difference between a 1.5 and a 1.7 rod ratio (the reason for the long rod setup). The biggest "advantage" woud be to run an off-the-shelf H or I beam rod (like a 6.0 chevy) and a short skirt piston with a high pin that would reduce friction somewhat and still be stable in the bore. This has to be offset by the cost of the modifications (crank mods, rod and piston cost). As for messing with a 5.09 vs 5.154, there is no perceptable advantage.
1967 Falcon 4 door 351C - 70 Mustang 351C
Owner built, owner abused.