Spark plugs Does my 1996 GMC Sierra 2500 with 305 engine take special spark plugs, and how long should they last?

Yes....10 years or 120,000 miles
Condition
Some customers of 2007-2009 model year Chevrolet Equinox and Pontiac Torrent vehicles equipped with a 3.4L engine (LNJ), and 2008 Chevrolet Express, Silverado; GMC Savana, Sierra vehicles equipped with a 4.3L engine (LU3) may comment about rough engine operation and the illumination of the Check Engine Light. This may be caused by spark plug wire boots that do not provide a sufficiently robust dielectric seal to withstand the high voltage required to fire the spark plugs.
Special Coverage Adjustment
This special coverage covers the condition described above for a period of 10 years or 120,000 miles (193,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. Dealers are to replace all spark plug wires and, if necessary, the spark plug. The repairs will be made at no charge to the customer. For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after January 5, 2011, are covered by this special coverage and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to January 5, 2011, must be submitted to the Service Contract provider.
Vehicles Involved
Involved are 2007-2009 model year Chevrolet Equinox and Pontiac Torrent vehicles equipped with a 3.4L engine (LNJ), and 2008 Chevrolet Express, Silverado; GMC Savana, Sierra vehicles equipped with a 4.3L engine (LU3).

Check the timing and make sure the battery is good, the battery can sometime have the power to crank the engine but have internal problems that leave it without enough voltage to give you a hot enough spark to start the engine.
You could also have some bad ignition parts which could be shorting out your spark or sending it to the wrong spark plugs. Plus you could also have fouled spark plugs.

Cap and rotor, spark plugs and wires.

1--6--5--4--3--2

did you check for spark to the plugs?...if you have spark check the timeing chain could have jumped time

You need to check for spark. You probably do not have spark causing the engine to flood. Check your ignition parts and see what shape they are in. If you have not had a tune up in 50,000 miles you may want to start there.

Doesnt this engine use a crank position sensor? mounted on timing chain cover.I would check that first

try changing the spark plugs and spark plug wires that may help...but first to be sure try following the ignition system from top to bottom...first try holding a spark plug wire half an inch away from your engine block and let somebody else try cranking the engine if you can't see a spark then try that with the wire connecting the coil with the distributor if there is still no spark than the coil needs to be changed

there are 3 solutions, 1, the distrubter, 2 spark plug wires, 3 power supplie to the coil pack (as in the wiring harnis )

there are some special pliers for removing spark plug wires.