If you look at pics 1 and 2, they provide the firing order and cylinder location (cylinder 1).
If the spark plug wires were not removed, the firing order shouldn't have changed. Take a look through this link. It discusses the most common causes of a backfire.
As far as the timing chain replacement, pics 3 and 4 provide the directions and show where the marks on the sprockets should be.
Let me know exactly what is happening. If possible, record what is happening and upload it for me to hear.
Also, I want you to check for diagnostic trouble codes. This vehicle has an OBD 1 system. You don't need a scanner to retrieve codes. All that is needed is a short jumper wire or even a paper clip. Here is a link that explains how to do it:
Let me know if any of this helps or if you have other questions. Also, let me know the codes you find.
See pics below.
Images (Click to enlarge)
Wednesday, April 7th, 2021 AT 8:34 PM