'71 340 balancer with forged crank

In my '69 Dart, 340 ('71), 4 speed I have vibration at about 2000 RPM sitting still and I think I may have an incorrect balancer. I'm wandering if the previous owner may have installed the wrong one. I rebuilt with same pistons and crank (forged). Can someone show me a picture, diagram or explain what the correct balancer looks like? I know the balancer for a cast crank is marked as such. Thanks for any help or suggestions you can give.