You really need a timing light to be right, however there are ways around it. If your problem is timing though it should not be causing excessive gas as you say. To time it without a light you have to bring the engine to top dead center on the compression stroke of #1 cylinder. You should pull out the plugs wo you can turn the engine easier with a socket on the crank bolt. You can either put your finger over the #1 plug hole to see if you feel a puff of air come out as the engine comes to tdc or you can put something like a screwdriver down the hole and and wait for it to come out as far as it will. (be careful here not ot get it wedged because of the angle of the plug hole). When you get to that point your dizzy rotor should be pointer to it's #1 position. If all of these are lined up you are at tdc. Now you need to loosen the dizzy and line up the reluctor with the pickup. That would be the star wheel in the middle of the dizzy shaft should be passing the the pickup right at tdc. To advance the timing from here turn the dizzy so that the pickup and star wheel line up then the timing mark on the balancer is at about 10 btdc. Tighten the dizzy and start it up. If it appears to run pretty good the next step is trial and error. Drive the truck and go pull a hill or somthing that puts a load on the engine. If it doesn't ping go back and bump the dizzy a little further to the advanced or btdc side. Keep going until the engine pings under load and then back off just a little till it goes away. I say again though that this should'nt have anything to do with getting to much gas unless the condition you are trying to describe has the timeing so screwed up that the cylinders are not firing at all close to when the fuel charge is ready. Good luck.