1968 340 harmonic balancer and main pulley

MoparMike1974 said
You should also know that not all 340's were internal balance. The good thing is the external balance 340 balancer says right on it "use with 340 cast crank only". 72 & 73 340 were external balance. May have been some early 72 that were internal.

Good point. less cam, smaller valve heads and external balance. Horsepower was on it's way out. Emissions was in.