Rv 440 + 6-71 ?!?

Thank you for all the insight. I appreciate all the comments. I will definately go with the double keyed crank. I have a hub as well. I was going to use that as long as I could get the rotating assmebly balanced internally. If it has a cast crank (late 70s) that may be a problem getting it balanced. The more I think the more I want to spend. At least new pistons on the mind...