Ignition/Spark Firing Sequence needed?

Sorry, my truck is actually automatic. It says manual in my profile info. I was going to change my spark plugs, wires and distributor cap on my truck and was confused about the current configuration (I'm the third owner, my first time doing this). I made a diagram of my current wiring configuration, and it looks like it has been setup for a 5.0l engine this entire time! I double checked my work, and here is the current firing order on my truck:1-5-4-2-6-3-7-8.

According to my Haynes manual, it says "255, 1993 and earlier 302 (5.0L) and 460 cu in (7.5L) V8 Engines = 1-5-4-2-6-3-7-8". Which is exactly how my wiring is set up. This does not match my engine type.

And for 5.8L Haynes says "351W (5.8L), 351M, 400 and 1994 and later 5.0L V8 engines = 1-3-7-2-6-5-4-8". My truck is a 5.8L so shouldn't the above order be correct? So, sanity check, sounds like the previous owner or their mechanic used the wrong diagram? Or am I reading the Haynes manual incorrectly? Seems like a no-brainer here but wanted to get a second opinion. And, perhaps unwisely, I reconfigured my wires to the 1-3-7-2-6-5-4-8 order just to see what would happen and the results were not pretty. The truck shook pretty badly, and the rpms were very low, 4 or 500. I turned it off very quickly. Very confused. I'll also say that my truck is running fairly well, the reason I wanted to change my plugs is because my acceleration at higher speeds is not great and gas mileage is pretty bad, maybe 8 or 10 MPG. I should note that I'm sure the engine hasn't been swapped by the previous owner. I added an image of motor top where it says 5.8 9n the top of the engine. It should be around 13. Thanks for any help!