[83GMCK2500]

Vacuum tubing should be available over the counter at any auto parts store, just need to size it correctly. Vacuum tubing can be sized in increments of 32nds of an inch, I'd just make sure it fit snug and didn't leak. I've always maintained this portion of my '83 and I find that it runs well and performs well from cold-hot.

I'd be surprised if there was an original/NOS one of those vacuum tubing harnesses laying on a shelf somewhere, but I suppose it is possible. If you want to find on I would suggest, looking for a user on here named "Hatzie" he's got a link in his signature to many .PDFs including the original parts catalogs. You can use them to find the part number and then go hunting.