I've been following the ambulance builds on ExpeditionPortal.com. The Medium Duty ambos (either Freightliner or International) have a 14ft box but plenty of weight capacity. The box can become an RV with some changes, can carry the bike if needed, can tow an RV if a hitch and brake circuitry is added, and has LOTS of storage to carry tools, and all the stuff that won't fit in the 26RR. Can't afford the Volvo truck so this is my next best.
Used ones are affordable also. I have a year of dreaming to go yet.
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Saginaw Valley BMW Riders