Won"t hurt a thing being a standard shift car.If you are that worried about it load it up backwards and tie off the steering wheel. Been done for years and still being done today.If it was a high dollar car I would get a trailer but its just a Corvair.
If you Corvair hasn't been driven for a while there won't be enough lube insided the 1st and 2nd gears on the output shaft and the trans will likely be damaged. The cluster gear does not turn when towing and the turning cluster gear throws the lube around the trans case under normal driving. Leaving the trans in 4th gear with the clutch pedal pushed down and held secerely would work on a short trip. For anything other than a short pull, 20 miles or so, rent a trailer.