I can't remember ever having any power limitations with the 230/420 in my 1965 short step-side.
Of course, that was back in the days of 55mph speed limits, and most of my driving was on forest roads anyway.
No clue what the axle ratio was but probably 3.73 if that was stock. I think that I was running 7.00x15 and/or 6.50x16 light truck tires. Seems like the gas mileage was around 15 but I didn't calculate it very often because of all the short haul driving. Anyway it was way better than the 1971 K10 350/350 that we had at the same time.
I've always had pretty good luck setting timing by ear. Always seems to run
better than setting to some spec with a timing light.
