Molnar Technologies 4340 Forged Steel 470" 3.91" Stroke 383-400 "B" Block Stroker Crankshaft - New

With the difference between a 6.535" B length rod and the 6.76" RB length rod on a 3.91" stroke you're looking at a 1.67 rod stroke ratio vs 1.73 rod stroke ratio.

The first thing in deciding this is your intended use. If it's a track only engine then I would probably go with a 6.76" rod to get a lighter piston.

If it's a street engine you could go with either length. I would most likely let piston availability guide my length choice over anything else and try to avoid a custom piston due

to cost and the time frame when ordering them.

Thanks for asking,
Tom