I did this in 2011 for my 30th birthday with my 2000 Boxster S, except it was it 60 days exactly.
NYC -> Nashville -> STL-> Chicago -> Sioux Falls -> Black Hills -> Denver -> Rocky Mtn NP -> Moab -> Arches NP -> SLC -> Star Valley, ID -> Jackson Hole -> Tetons -> Yellowstone -> Missoula -> Glacier -> Nelson, BC-> Osoyoos -> Vancouver -> Victoria -> Salt Spring Island -> Bellingham -> Seattle -> Portland -> Cape Arago, OR -> Redwood NP -> Ukiah, CA -> SF -> Santa Cruz -> LA -> San Luis Obispo -> Big Sur -> Carmel -> Yosemite -> San Jose -> NYC (by air, car transported)
No motels -- mostly camping, hostels, and staying with friends old and new.
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"Betty" -- 2000 Boxster S, Triple Black, loaded except PSM (sold to a good home)
"Veronica" -- 2008 Boxster S, Arctic Silver on Blue
"Maleficent" -- 2007 Cayman S, Red and Black, TPC Turbo 3.6L 460 RWHP, H&R RSS Coilover / TPC stage 2 suspension