I had mine rebuilt by D&D and the timing mark was OFF TDC. Had to remark it.
Check out TA Performance. They may have harmonic balancers, I don’t know but I doubt there’s a diff. I’d go for a new balancer vs. rebuilt if available. They are willing to talk and have good info. They specialize in Hi-po Buick engines including the 215. They carry the correct oil pump gaskets, pumps, including HV and a booster plate for the pump, and a shim gasket kit for the oil pump so you can get the bottom plate clearance correct. Also new front covers of the Rover type so be aware they don’t have the generator mounting bosses.
I sent mine to Winslow MFG http://www.winslowmfg.net/ and they rebuilt mine. I had them do the one on my other Jetfire and was fine, I had them do one for a 70 442 W-30 and it came back off about 10 degrees and had to remark it. I have not been able to check this one yet and will be later this summer before I can.
I have had three Jetfire harmonic balancers restored by the Dampner Doctor in CA. They have all been returned with the timing mark correct. As I recall, they need your correct core and restore and return. My last 1962 Jetfire balancer was from an engine that was never taken apart and was original from the factory. Not inexpensive but they do a great job. https://www.damperdoctor.com/