Jerry, we''ve cruised outside the U.S. for a while now (tho'' not in the Pacific – yet?) and here are a few of the criteria I would recommend to you for selecting a boat to do a Circle, almost independent of budget and boat ''size'' (as measured by displacement more so than length):
1. good load carrying capability, without seriously affecting the stability, speed or comfort, along with functional, capacious storage (both inside and in the cockpit)
2. decent light-wind sailing ability (in e.g. E Pacific, the Med, during your ITCZ crossings), but seaworthy in a real blow (e.g. when dipping low to visit NZ or perhaps around S Africa)
3. excellent cockpit ergonomics (you’ll be there a LOT) that provides good protection (from wind, wave and especially sun), either via canvas work (consider a hard-top type dodger due to U/V & Strata-Glas panels) altho’ boats with deep cockpits & hard dodgers are probably better
4. a layout easily navigated when the boat is heeled and moving actively, and which offers a good sea berth for each crew member, a functional galley, a head not located too far forward in the boat, and a sit-down/comfy nav station
Based on the above, I would not put a Cape Dory high on the list. She has a relatively short waterline, lots of wetted surface, and somewhat narrow ends, so her light wind ability will be limited. And while any boat can be loaded up deeply, I think she’d struggle with the consequences more than many others. I also think her traditional cockpit is less ergonomic than you’d prefer.
That still leaves a huge range of used boats available for consideration, just a few being a Sadler 34, Tashiba 36 (or smaller 31), Tayana 37, (Maine-built) Mariner 36, Caliber 35/38/40, Pearson 38, and a Fast Passage 39 to mention just a few – all of which are different from one another in many ways. Keep in mind that people have sailed long distances in deep water in almost anything…but that doesn’t recommend almost anything.
As for equipment, any good ocean cruising guidebook will give you the important basics: consider consulting Beth Leonard’s Voyager’s Handbook, as it covers the equipping of a boat relative to one’s budget (always an issue for cruisers, it seems) and is based on her own Circle experiences. A really stout, functional anchoring SYSTEM, a range of good sails needed for the diverse conditions, an upgraded DC electrical system if you put gear aboard that will require it, and - speaking of that - a water maker and deck water-collection system (for the Pacific Islands and other select areas like Greece) are all probably good ideas.
Good luck on the shopping…