Originally Posted by Rineholio
If you put the cam in correctly then I think your distributor is off a tooth, making your timing way off. Have you checked the timing? Put #1 at TDC. Make sure it's on the compression stroke. See where the rotor is pointing. I wouldn't fire it up to check the timing until you do that.
I'd also recheck the plug wires once more. Maybe one is swapped. The backfire makes me think it has something to do with ignition.
yes, i did put it at TDC on compression stroke and i set the distributor body to line up with the rotor. but when i tried to start the truck i had to turn it a bit counter clock (advance?)to get it to run at all. i just rechecked the wires again and they are correct.