You might want to reverse the numbers on your bottom line. if you replace your 30a breaker with a 20a breaker its probably going to trip a lot. Do not replace a fuse or breaker with a higher rated one, you risk melting the wire its there to protect. You could ruin your harness, or have a fire.

1961 ford f500
1953 3100 five window (https://www.facebook.com/1953-Chevrolet-5-window-1533405913413610/)
1955-2 3200 big window (https://www.facebook.com/Leep3200/)
55yrs as a mechanic and retired. (kind of)