The topic of ether usually brings out folks who state that using it will totally trash your engine. When used sensibly, that is completely unfounded advice. When you get into engines that are 8-9L and larger, the number of engines that used preheaters start to dwindle pretty fast. It takes a tremendous amount of energy to heat up enough air to make a difference for engines that large. Ether is the cold weather starting aid of choice for most engine manufacturers of large displacement (there have been millions and millions of engines built which were equipped with ether start from the factory).
What is being done today is an integrated solution using ether. There are a number of engines that monitor crank speed after start up and will inject ether while the engine is running if crank speed drops below a certain threshold or begins to osculate. This is done for idle stability and white smoke clean up.
But back to your oliver....as other have stated use ether or preheat, but not both.
If your preheater is weak or not working, an option would be to look up the ether kit used on the CaseIH Maxxum series (5140, ect.) You'll need to put an 1/8 npt port for the nozzle somewhere at the entrance to the manifold. Ether is nice since it makes for quick starts and won't drain a weak battery even before you crank the engine over.