I need some advice on the crankshaft. 1973 340 started smoking and running crappy. So I decided to pull it apart and try to rebuild it. I got the trick flow heads, ordered the lunati roller cam and lifters. So now most of my money is gone. When I got to the crankshaft, the bearings and crank were shot. Scores that are pretty deep in both the main and rod journals. So I need a new crank. Can I just buy a mopar external balance crank and just put it in or do I need to get it balanced. I'm not going to be racing just some burnouts around town and some highway use. Did these motors come balancer from the factory?