A TVD (tortional vibration damper) is used to stop HARMONIC resonance inherent in a gas motor. Every time the ignition fires, and forces the crank down, a resonance is built up in the motor. Think of hitting a pipe with a hammer, it rings. But when you touch the pipe, it may sting, but the ringing is dampened. The rubber ring in the balancer acts the same way. It absorbes the harmonic virbrations generated in the crank from the hammer blow of the ignition firing.
Running an engine without one can be deadly. The resonance never gets stopped, and... kinda like the fat lady busting a glass by singing.
But don't panic. I think the reason 3's don't have one is based on the low rpm range, bore*stroke characteristics, metalurgy, and the heft the engine was built with. (ever see the size of the bearings in that motor?) All these things have to be taken into account to determine the frequency something will vibrate at and when.
I don't know if somebody makes one or not, i'd guess so, last vintage race I was at, I know that motor was revving higher than 4500.
Hope this helps.