What block and what application? Street, race or both?
How big are you wanting to make the motor now? Which heads, intake and cam type?
I've built some SB stoker motors for both race only and street and strip using from 3.750 stroke up to 4.00 in both 340 and 360 motors. Mopar use to sell a good forged 3.79 stroke race crank with the 8 bolt Hemi rear flange that should take a lot of abuse I would look at using a crank with SB Chevy rod pin sizes and a good after market race rod with either 6.125 or 6.250 long rods