1994 Chevy Blazer Timing

Engine Mechanical problem
1994 Chevy Blazer 6 cyl Four Wheel Drive Automatic

We have a problem that we believe may be related to the timing. The truck will not start. It will begin to turn over but then it acts like the battery is dead and it starts to back fire. We tried moving the timing a little bit at a time and got it close to starting but still would not completely. What is the likely hood that it is soley the timing and if it is just the timing, how do we know where to set it so that it is in the right place. Please help. This is our only mode of transportation and we need it back very desperately. We have had serious chugging and backfiring problems so we tried switching the distributor with another used one. This is how the timing got off. We have also changed the oxygen sensor, the spark plugs, spark plug wires, and the distributor cap. We cant afford to fix anything else. Please help if ya can.