I am trying to locate a 1911 REO Truck for my husband's 40th birthday.
 The REO was in the Fizzell family but was sold through Ron Fizzell
(my husband's father)in the late '70s/early '80s near Lansing, MI.  We
believe the gentleman who bought it was from Pennsylvania.  Ron
Fizzell has since died so we don't know the details of the sale.

Can you refer me to people or organizations that might have
information about this type of vehicle?

I would suggest a) contact the PA Dept. of Motor Vehicles. Many DMV's
are able to do a vehicle search. b) here is a link to stats about that
truck http://www.conceptcarz.com/vehicle/default.aspx?carID=7484&showID=42
c) and here is an auction that was held in Florida in 2006;
http://www.carcollector.com/marketjournal/RMAmelia2006CCOnline.pdf
This is a .pdf file. They had a 1911 Reo truck which is shown at the
bottom of page four. I've posted the piece at
http://www.97330.com/1911_Reo_truck.html

Here is a link to Reo Registries 
http://www.hemmings.com/clubs/results.html?make=Reo

You could also run a classified in Hemmnings Motor News
http://www.hemmings.com/classified/place_classified/create_classified.html