If the battery is good and fully charged but the engine will not turn over then either the starter or the ignition switch is defective. Or you have a loose or corroded connection.
you should be able to start your jimmy up right after you install your new battery...if it doesnt, I would replace or clean your battery cable terminals and see if that works!
A battery jump starter works by taking the charge from another battery, such as in another car, and passing it to the dead battery. When the charge is sufficient in starting the dead battery, it should then start charging itself as the engine runs.
Sounds like a connection problem from the battery to the car. Easiest way to find out is to get a jump start from another car, if it works then it's the battery, if not then is either the battery cable or an alarm/immobiliser that is still armed.
As long as the alternator works and your charging system is correct, the new battery will start your truck and keep it running.
You Need a 35 Series BatteryThe best answer I can offer is that you need a battery that is a 35 series. They vary from brand to brand such as in Wal-Mart, the brand "EverLife" requires size 35-3S. At CarQuest, it is a 35-84 battery is the size you need. Everything I read says that it works for both a '91 and a '92 Ford Escort (all types).
Dead battery? Loose or corroded battery cable? Blown fusable link?
it works in side the battery
http://www.batteryinternational.com/lantern-battery.html would be a good place to start. If that doesn't help then call 1-877-28-BATTERY and they should be able to find a battery replacement that works for you.
Double check that the battery works, then check if the engine works.
how does a battery work
That all depends on whether or not you turned the key on with the battery t erminals reversed. I did this once and nothing happened except that the ammeter showed a disharge while it was actually charging. I think you have changed the polarity on components of your vehicle. I'd put them back on right and see if it will start and see if everything works all right. If you had the cables reversed while trying to jump start a car it will Fry everything.
Buy a new one if you can't replace the headset's battery, as the battery is dead.