Cast crank with JW flexplate?

Just traded into a running 78 440,452 heads, and cast crank. I'd like to run this thing in my chassis car for alittle while in front of the glide' but I dont know wheather there would be any problem with using the JW flex plate with the cast crank. Can I do this?

Cast crankk 440's were externaly balanced with weights on the conv. I would guess that neither your PG conv or JW flexplate are weighted for an externally balanced 440.