Magnum mount issue?
Well 340's with forged cranks where internally balanced cast cranks which are 72" and 73" I think are not.
I'm runnign a 360 which was supposed to have been internaly balanced at the time of rebuild but due to paperwork errors wasn't. So it had a BAD vibrations with rpm.
I had an aftermarket balancer that had weights swappable for different small block applications so I put the weight in it for an external balance 360 and it got much better so now I need the weighted torque to match.