Years ago during my restoration, I had the same dilemma, use repro vs. NOS. I bought repros and did not like the way the ends were cut sharp. I bought NOS felts for my RS 69Z: P/N-7755881 and 7729998 door inner and outer, and 1/4 window LH 7725923, RH 7725935 outers and 7642401 inner felts (I saved the original GM packages but did not mark exactly what was what so I may be wrong on what is inner vs. outer part numbers). Here are pics of NOS door and 1/4 window felts.
Jim Stubbings, owner of Heartbeat City, 586-226-8811,
www.heartbeatcity.com, has a large inventory of NOS parts and may have a set of NOS felts.
I don’t recall if all felts were the same. Did the standard and deluxe interiors option cars receive the same felts with the stainless trim on both interior and exterior felts?