Xtra plugs and your usual gas. U could bring ur timing light but that's like bringing toothpaste to a dentists office, aka you shoulnt have to. But u need to establish who's gonna be tuning it. You or them.

A wideband bung for each bank would be good. I'm not a fan of tailpipe sniffing.

Biggest and most important advice is to fix ANY existing issues you already know u have before you go. Once EVERYTHING is in order to the best of your knowledge then you hit the dyno and if there's any other issues that you can catch because it's on the dyno then try to be prepared aka bring your jets like you mentioned.

Other than that you should be good