Car guys love to help whenever they can. Sounds like you went the extra mile to help these guys. Well done. Just to add a little something else which may open a can of worms. I built a 440 with headers and the motor never liked to start when hot. Could always hear starter struggling. I had the bigger starter and had been freshly rebuilt. Actually came out of a Police car. I eventually went to stock 440 manifolds and never had a starter issue again with the same starter. That starter is over 25 years old and I just replaced it with the mini starter.