[Accelo]

I have the Classic Update Kit.
If your truck is stock it would be better/easier to purchase the OEM matching harness.
To install the Classic Update Kit you will need a special crimping tool that folds the ends of the connectors in like the factory did. They are not the cheap ones at the auto parts stores.
The Colors seem to match the factory colors.
Typically one end of the harness is finished and you have to to the rest. No it's not that difficult but is sure is time consuming.
I would recommend it if you are modify your truck like installing an LS motor our moving the gas tank. Also includes some niceties like a wire to convert your cargo light into a third back up lamp.
Yes, wiring for the whole truck in included.
I believe it is set up for a HEI. (only difference is no resister wire needed for the HEI)
Do I have to assemble it? Yes some assembly is required. Actually quit a bit.
What about internally regulated alternator? This I don't know about. I suspect it is customizable but I haven't opened the engine harness yet.
Cheers.
Rick