one thing in a previous post that i think everyone overlooked is he mentioned that it backfired and it appeard to come from the base of the carb, and that the carb had been removed and reinstalled, 2 things i would check first, i bet you have a HUGE vaccum leak at your carb to manifold gasket get some dish soap and put about 2 spoonfulls into a 16oz spray bottle and fill with water, spray it all around the base of the carb and try to start the truck, IF it runs continue spraying around the base of the carb if you have a leak the rpms will pick up and it will suck in the soapy water. check carb base and intake manifold mounting area for warpage if its good replace gasket. second check your float setting and make shure its not flooding the engine. now if all that is not the problem lets go to the basics an enigne needs
1, Fuel
2, Ignition
3, compression/correct valve timeing
if it has been starting and running we can assume it has some compression a good test for compression and valve timeing is get a vaccum guage hook it to manifold vaccum like the brake booster hose disable the ignition remove coil wire, pull fuse whatever it takes, hold the throttle wide open and crank the enigne for 5 seconds while watching the vaccum guage it should read 1-2 inches of vaccum and may bounce slightly. if it is below 1 inch you may have low compression or bad valve timeing but i dont think that is your case. reconnect your ignition
check the ignition next, pull a spark plug reconnect the wire and ground the threaded part of the plug to intake manifold or some other non painted surface on your eninge crank and see if it jumps the gap on the plug or if your a thrill seeker grab hold of the plug wire with your hand and grab anything metal onthe truck and crank it over nothing like 20,000-60,000 volts to start your day, if the engine fires it will sound funny but its not damageing anything reinstall plug if you have spark
Fuel, granted your 1 year old fuel filter may pass fuel but it may not be enough volume to keep it running or your fuel pump may be bad i highly suggest getting a good fuel pressure guage kit that will test pressure and volume follow the directions with that guage for testing your pressure and volume.
as far as your electrical problems invest in a decent multimeter like a fluke meter and preform a voltage drop test on all your battery, starter, and ground cables
here is a good article on starting system diagnosis and troubleshooting
http://www.prestolite.com/pgs_training/training_4.php
hopefully this helps and might give you somethign to work with, if all else fails check local comunity collages for a good automotive program and see if they have a tune-up class that could tackle your problem might take a while but its VERY cheap and everyone gets to learn most schools will let you watch the class troubleshoot your car/truck good luck!