I tried changing my spark plugs and wires earlier today. Looks like the plugs were the wrong size (I order off amazon and ordered AC Delco but they are much longer than the ones in the car and the neither wire boots fit around them).

Anyway before I went any further I put the three old spark plugs I changed back in the car. I tired changing all of the wires (Taylor) but none of them would snap on the old spark plugs. So I put my MSD Street Fire wires back on and can get each wire to snap back on except for #5 and #6. They will go on the distributor Cap with no problem but not on the spark plug.

When I start the car I get a loud pop and bang. I'm afraid to leave it running for more than a few seconds in case it causes damage. Any ideas of what to do?

I thought I got both wires to snap on. I fired up the car and no banging noise but rough idle. The entire car was vibrating. I moved the car under it's natural torque and when I stepped on the gas it backfired.
I parked the car in my drive way. Killed it, and sure enough #6 wasn't on and #5 was on but really lose, I don't think it ever snapped.
I'm assuming the backfiring is caused by missing two cylinders.

I can't believe two spark plug wires are causing this much frustration.

Put some dielectric grease inside the boots so they can slide on without binding. Push and wiggle till you hear the click. If your boots are straight, you can push the boot further onto the wire, snap it to the plug, then slide the boot down onto the plug. With 90* boots about all you can do is make sure the socket of the terminal is facing the open side of the boot, and that its approx centered in the boot, so it's not fighting you to line up with the plug.

I'm using a small tube of dielectric grease I have. They are 90* boots. I just can't get them lined up for the life of me.