1991 ford econoline workvan

Recently bought this van but owner had lost the keys, how do I go about removing ignition without the key

If you take your registration to the ford dealer they can make a key. Call about the cost before you go. Lock smiths can make you a key call one about the cost. Figuring the cost of a new switch and time to install it try this first.
If your key is on the column you have to remove the steering wheel to replace the tumbler. Check the cost before you decide what to do.