Might consider replacing the points & condenser with an Ignitor module and using a high output coil. Remove the resistor ballast wire and run direct battery voltage. Make sure ground cables and connection to the block is clean and tight. I even run a cable direct to the cylinder heads, and then bond them together. The idea is to provide for hottest possible spark, the key to efficiently burning leaner fuel mixtures. If the ignition is weak, especially under load or high speed, it will only run decent with an overly fat fuel mixture.

A sloppy distributor with high mileage will often cause a cylinder or two to ping or knock requiring the entire ignition advance to be detuned or retarded. The problem with trucks is they have the aerodynamics of a brick and are heavy. Properly geared a bare bones V8 in a car will realize 20 to 25 mpg on the highway with a good timing curve and a setup vacuum advance, and carburetor jetted and setup correctly. A jet size change flows about a 2.4% difference - and there are two in a Autolite or Holley - so if you can jet down the fuel consumption changes are pretty easy to pencil out.

The key to mileage is to lean out the fuel air mixture on the highway when cruising on level ground in high gear. Engine load is practically nonexistent under these specific conditions. At the same time, the vacuum advance pulls in mucho extra ignition timing due to the high manifold vacuum. Here again, a hot ignition spark at the plugs is required. Lean fuel mixtures are safe during level cruise. Modern fuel injected engines run as high as 18-1 AFR, this is not possible with carbureted engines, but with careful tuning around 16-1 is right as rain and will return the best mileage. Interestingly if the fuel mixtures are too lean, the fuel mileage actually starts to decrease. It will run excessively hot.

The danger to keep in mind though is whenever the engine is under acceleration, under load, under power, wide open throttle etc, the air fuel ratio must be well on the rich side of things. Lean fuel mixtures under these conditions, WILL burn valves or holes in the pistons. Think of how an acetylene torch flame acts when you dial in the O2. Same thing inside your engine.

If you want to tune for mileage a wideband O2 sensor is the way to go. I was able to jet way down and pretty much double fuel economy. This also required drilling out the PVCRs, these are sort of like fixed jets, under the power valve. The power valve determines when extra fuel is provided under acceleration, not how much. As always the plugs will still tell you how it's running. It is a lot more difficult with modern fuel, but there are important cues to look for. Deep inside the plug, where the shell transitions to the porcelain, is the color ring to look for. This is where the wide open throttle fuel mixture can be observed. The ground strap shows both heat range, and ignition timing. The first few threads and the base ring shows cruise jetting. Using a hotter ignition and leaner fuel mixtures might need to step down to a slightly colder plug. If the plugs are running too hot it can start to ping or knock due to pre-ignition even if the timing is correct.

Keep the fuel fat under power and acceleration and lean it out on the highway and your engine will be very happy, your wallet will thank you, and you won't need a fuel truck to follow you around.

I've used the basic Ignitor, the 1281 for a long time. Ford used the same points from '57 to '73, even for sixes (I think) so the 1281 should be the one. It's $67 if you shop around, not too bad. You can use the existing distributor, cap, and wires. You can use the stock coil too if you want.

The factory stock sizes in the shop manual are where to start. Make sure everything else is right, like fuel pump pressure, fuel height, no vacuum leaks. What do your plugs look like?

Yeah I wondered if it was the same, though the points were the same for V8. I put together a points distributor as a spare to throw behind the seat just in case the Pertronix ever dies on the road. Well it works good, but the difference in spark between points and the Ignitor at the plugs is noticeable when you look at a grounded plug in the open air. I use the 1.5 ohm epoxy flamethrower coil too. The only thing if you go this route everything has to be in good shape, cap, wires, rotor etc, good quality. The spark plugs will always only "take what they need" in terms of firing voltage, but running straight battery voltage to the ignition coil does boost everything up a notch. High quality plug wires are a must. If there is a weak spot in the ignition components, the higher ignition voltage will find it and arc to ground.

Most often distributors are just mechanically worn out by now, with a whole lot of shaft wobble or sideplay. Points don't like this at all, and the (dwell) ignition timing will be erratic. The Ignitor module is electronically triggered by magnets and so is a lot less affected. If you can find a fresh distributor though, I would recommend that even when running Pertronix. If you want to stick with points though it is really critical.

6 cylinder engines Pertronix reccomends a 3 ohm coil. The classic Bosch Blue coil is really good at a good price. That would be run with straight battery voltage to the coil.

Yep, use a 3.0 ohm coil with direct voltage meaning no ballast resistor. In Fords for many years it was part of the wiring harness aka "pink wire" from the ignition switch. Disconnect that and replace it with a heavy gauge wire from the switch to the + pos terminal of the coil. I have heard better things about the Bosch coil from people who do that stuff for a living. Just make sure it's a 3 ohm coil though whatever you decide on.