I store my 73 with about 5 gal. of race gas (it doesn't go sour as quickly as pump gas) in the tank and with the car on the tires, have not had a noticeable problem with flat spots. If your storing on cement in a non heated building you may want to park it on sheets of cardboard or plywood (barrier between floor and car) to keep the condensation and rusting to a minimum. Our car only gets around 5 or 10 miles a year and I've been storing it like this for 10 years now (since we quit racing). I've thought of putting mine on jack stands, but wouldn't be able to move it quickly if I needed to. (think fire)
By the way, thanks for serving and take care over there!