53, Yeah, I have used the jacobs stuff. I was very pleased. Mileage increased from something like 7 to almost 10. But it is worth noting that I was using an original points dizzy and factory coil before the switch. I installed a duraspark dizzy and wired it to a chrysler LX101 box, and then through the Jacobs unit, and used a jacobs 380672 coil. The instructions are in Jacobs' book. Whether or not the improvement would have been as great from changing from stock duraspark to Jacobs, I don't know. I was not looking for mileage at the time, but better cold weather starting and driving. It did that exceptionally well, I still have that ignition on the truck. With the plugs gapped at .080, it starts immediately and never hesitates, even in sub freezing temps. What ignition do you have now ? I think you might want to look at your axle gears before you spend any money on the ignition. 3.5s are WAAYYY too much help for the 460, especially with such small tires. One of the other employees at the shop I'm with runs 35 inch tall tires with 3.5 gears in a '78 F150 4wd, and his 460 has no troble moving the truck or even pulling trailers. What axle do you have ? If you have a 9, maybe you could borrow a set of 3.00's or a 2.75, and see how it does. Can you borrow a pair of rear tires that are 35" or bigger ? That would give you an idea how the engine will behave without so much torque multiplacation in the axle. DF, @ his Dad's house

 

Dino,
I have the Jacos on now. I am running a stock Ford points type ignition with an Ignitor set up instead of points. This is routed through the Jacobs system. One thing I forgot was to re-gap the plugs. I'll take care of that later today. I would guess that will have a dramatic effect. As for the gears, I am not in the same croud I was a few years ago, and no longer have access to 9" rearends at a whim like I used to. I would love to put in a 3:00 rear, but again, I have no access to one, and am not willing to buy one at this point in the game. I am moving next Saturday. This move is cross country, so that is why I was asking the questions in the first place. I like the acdceleration of the 3:50's in the rearend, and I will be racing the truck when I get to Fla., so those gears are about what I need. for a dual purpose truck. I USED to have a 3:00 rearend just laying around, but about 6 months ago, I decided I would never use it (DOH!) and threw it away. DOH!!!!! Oh well....The 3:50's keep the truck at around 2500 RPM at 60, which isn't too high IMHO, and gives me the torque I need when hauling butt up a mountain pass.
Anyway, the mileage increase you mentioned is about what I got in my mustang, and also what I am now seeing with my truck. Before, I was getting about 13 MPG, now I am getting about 15 to 16 depending on how I drive it. Of course, I need to gap the plugs a little wider now, so I might get even more....Who knows....But when I start towing, my mileage will go down I'm sure.