Okay, when my optispark went out, the guy who fixed my car mentioned something about my harmonic balancer being damaged and ordered a fixer kit or something for it. Well, after that, whenever my car is anywhere from 2200-2600 rpm (doesn't matter which gear) it seems to roughen-up, the car seems to vibrate. It doesn't appear to affect anything, but it is annoying. It also does the same thing at between 80-90mph out of gear. Does anyone have any idea?

 

Got this write up from www.automotiverebuilder.com/ar/ar99928.htm
Hub and Balancer:
The balancer is a two-piece assembly with a pulley that bolts onto the hub. Separating the two made it easier to install the Optispark distributor on the assembly line and out in the field. The holes in the hub are offset, so the balancer only fits on it one way, but there’s no keyway in the hub to index the hub on the crank. This shouldn’t be a problem unless the damper was drilled at the factory to "trim" the final engine assembly.

If it was drilled a lot to compensate for an engine that was out of balance, you could end up with a shaker, depending on how everything stacked up with the remanufactured engine compared to the original engine. If you encounter a balance problem on a remanufactured LT1, try rotating the balancer assembly on the crank 90° at a time to see if it eliminates the problem