. I suppose this is because the static timing was retarded, at 5ยบ ATC. I don't have the CAP widgets, so I don't think it would be happy at that timing, and the curve problem would be worse
I have 2 CAP 67 distributers. I run both at 0 to 5 before. The nice thing is the curve is essentially the same but it comes in faster. But look at the all in point, it's about the same.
Mine is a tired 273 2 bbl and runs on 85 octane without issue, 85 at 5000 feet is equivalent to your 87 at sea level.