No engine shocks, I overlooked that one in my thought process. That being the case I would think the engine could be fitted with a stop strap. The stop strap will curb "engine hop/vibration!"

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When exactly does it vibrate?
How pronounced is it?
Is it during hard acceleration?
Does it shutter when starting off from a stop?
Is it at a constant speed?
If so, what speed?

I would think that flywheels are balanced seperately. I would also think that you should be able to fit a replacement flywheel to any engine without creating perceptible vibrations. I would also think that if a flywheel needed to be balanced to an engine/crankshaft it would be cost prohibitive to ever replace a damaged flywheel during a clutch repair.

My only real thougt about the different flywheels on these two engines is the difference in weight. I believe the 616 flywheel is heavier thereby affecting the rate of acceleration on the 617. It may also impact engine braking during a long, steep downhill descent. Would it be noticeable? geez

I am of the belief that if you are "rebuilding" an engine than it would be wise to have the engine balanced. The “Harmonic balancer, crank, and flywheel” are balanced to each other thereby eliminating any subtle vibrations that may, or may not cause damage.

Would it be safe to assume that the engine that went into your vehicle was a “recycled” unit with X number of miles on it?