I finally figured out my points gap was wrong because of a dwell meter from a yard sale
Spent two years chasing a rough idle on my 289 and re-gapping by eye every tune up. Picked up a dusty dwell meter at a yard sale in Toledo for $8 and found I was running 38 degrees when the book calls for 30, so that eyeball method was costing me 8 degrees the whole time. Anybody else learn a tune up lesson from a cheap tool they almost passed on?