Looks like a good score. A little more work and you'll have a trailer.
Then just have to get the correct hitch extension for your weight and you'll be golden.
Every stock pleum I've ever pulled the pleum gasket was blown. That 5.9 I just disassembled it was blown.
Enjoy the rig and will be 👀 for the axle swap.
Great that you got it running again... Bummer about the plug wire but as they say "Shit Happens"
And yes there is a TSB for routing of the plug wires. If you need it I've got it. Also have you put a new plenum gasket on? They way to tell if it's blown is to look down the throttle body and see...
I knew about the destroking a SBC too but wasn't thinking about that. Honestly had kind of forgotten it being an option since it's been a LONG time since I've even heard it mentioned.
When I was doing my exhaust I used tri-mix also for my gas & then some Solar Flux that you use on the joint you're welding. It's isn't as good as having Argon to purge with but from what I'd read it's better than nothing. I'm not that great of a welder so take it for what it's worth...