[kipps]

Most of the connectors on your stock harness are going directly to devices. Headlight switch, tank selector switch, fuse box, water temp sensor, tail-light bulb, etc. You'll be looking at large-scale fabrication if you intend to replace each of these with their modern equivalents. There's simply not a lot of connectors left that you can swap to metri-pack without redesigning the whole thing.

I'm working on something similar. I'm routing the dash harness to my own liking, using a modern fusebox under the hood, installing a ls engine, and changing quite a few things to match what I want it to do. Obviously, I'm using the original packard 56 and pack-con connectors at all the devices on the dash. I'm using metri-pack on the engine and fusebox stuff, since that was built that way to start with. Any new stuff will be metri-pack.

The hard part of what I'm describing is simply figuring out how all the connectors work, what tools are needed, and what and where to order. The other hard, but fun, part is reverse engineering both the '87 and the 2010 harnesses, and designing my own circuits. I expect the actual harness assembly to be a breeze.

Another caution, is don't just blindly assume your existing harness is junk. By the time you remove it, clean it up, inspect it, and figure out how it works, you'll probably realize it's in pretty good shape, and is actually trustworthy. I should have looked mine over better before shredding it. My main concern was the bad corrosion in the factory fusebox, from muddy boots, etc over the years. I could have bought a new factory-type fusebox, pinned my existing harness into it, and been far ahead. By the time I'm this far though, I might as well finish.