94 ram1500 4wd. 5.9 I am thinking about adding headers. Is it worth the effort? Hoping for more mpg, hp, and torque. It currently has dual exh. all the way out the back!

If your truck is stock you won't gain much if any.

Not as a bolt on alone, especially shortyies, I wouldn't waste a single $1 on a shorty. Long tubes might give you about 10-15 HP if the rest of the exhaust is done right.

MPG won't really change any except maybe at really heavy throttle angle where the computer ignores the O2S and it will lean it out a hair but it will be hard to notice without other supporting modifications.

Best bang for the buck is a cam swap. It makes a noticeable difference in power but wont help mileage. Didn't Hurt mine either though. For mileage the best improvement I have done to a truck was a tonneau cover. You could try either taller tires than stock or a gear change to get the rpms down as well.