Vance,
I’ll chip in…I just acquired a 67’F that sat for years! (The entire story soon). The A&P/IA seller rescued it and did a top IRAN on it and put a few hours on it before I bought it. No issues were found or present while he flew however after my 1st fuel stop and 3 hours of flying I had no issues in starting but afterwards for a bit it ran like some described, stumbling. I taxied to an area were I could clear the mags thinking perhaps a plug fouling. I was satisfied and did a static takeoff, it seemed to run fine. Did not see anything on JPI. 2nd fuel stop the same symptoms, perhaps not as pronounced. That 3 hour leg was fine and F is now home, well almost, temporarily parked at a different airport. The seller suggests adjusting the mixture again. I’ll be troubleshooting further.