Pretty close to what I have now...

Steel frame 4130 or one step up to 531 or whatever the current equivalent tube set is. Saddle will be a Brooks Flyer. "gears" whatever works the best for my situation at the time. I currently have one bike set up with older Shimano Deore LX, another set up with Suntour XCM. I have a third bike that I will be trying a Shimano Alfine 11 speed on soon. I use Nitto, Bor Yeuh, Blackburn and Jandd Expedition racks. For bags I have Carradice, Ortlieb, and Lone Peak at the moment. Handlebars range from steel north road style to no name alloy drop bars to butterfly/trekking bars.

There is no real one size fits all. My first long tour was on a slightly upgraded 1974 Motobecane Nomade that was mild steel gas pipe. The wheels were handbuilt by me prior to the trip using Wolber 58 rims and Sansin hubs. They are still rolling pretty true after 36 years and some 15,000 mile of riding.

You can tour on just about anything, for me it is more about the mindset rather than the equipment. I chose equipment based on value for my dollar versus the use I want it for.

I have several bikes and literally tour on all of them depending on where I am and where I am going. They range from a 1971 Raleigh Twenty folder to a 2007 Redline 5.3.1 fixed gear.

Aaron