Chevy & GMC Vans

for starters my computer is toast so i am at work and may not get on here again for a bit. anyways my van has had some issues that ive slowly been addressing in the last six months or so, ive also been doing a lot of body work to it when the weather permits. long story short i havent driven it in at least six months until last week. i was re-welding my exhaust and had it completely off at the manifolds. i was charging my battery at this same time, once the battery was charged i decided to see if she would fire up, it did no problem really. i then realized it had very little gas and figured the gas station is less than a mile so why not... it had little power due to the lack of exhaust back pressure but seemed to run fine. i also had to go into town to get one more piece of tubing for my exhaust but i took my truck for that. got home it was dark and the next couple days rained. finally had one nice day finished welding and bolted my exhaust back up but it would not start for some reason, i could hear the fuel pump, it was turning over but just wouldnt start. i happened to have a spare fuel filter so i changed it out but still nothing. my only thought is that running it with no 02 sensors could have fouled up my spark plugs to the point of no ingnition. sorry if this is hard to follow but does anyone have any thoughts? i am about to replace the injectors in my truck and need to get this thing running for at least a week. it never had problems in the past, but its been sitting for a while now so...

First things first...replace the cap and rotor and then possibly the wires and plugs.

3 things needed to run: Air - Fuel - Spark.
It is unlikely to be air, which leave fuel & spark.
Before proceeding to the distributor cap & rotor route as Dean has suggested .... add some fuel.
Do this by simply spraying some fuel (flammable liquid like brake cleans) into the throttle body or air intake snorkel.
Crank the engine & see what happens.
If it fires/sputters/coughs or runs, you will know that the ignition system is working & that the fuel system is the source of the problem.

well, i let it sit for two days thinking i might have flooded it, went out on saturday and it fired up first try. now it starts up everytime like it always has. i eliminated my cat, re-welded a couple problem spots on my exhaust and replaced the manifold to y-pipe gaskets and so far the SES light hasnt come on. it sounds far healthier than it has and seems to have re-gained some power.