While the OP’s post is for volunteering for historical preservation opportunities, I would also remind others there is other sources for Volunteering. Plus they have RV sites for Truck Campers and other RVs! Many even have reimbursement for expenses. So if you are interested in working at a BLM site in Southern Utah or restoring 19th Century Buildings, as well as working in Visitor Centers in Grand Teton National Park and many other parks in this country, click on the following link;
Volunteering in America's National Parks BLM and so many more, CLICKY !!!!!b