This store http://www.keylessride.com/default.asp has a method for checking to see if your Ford E350 is equipped with keyless entry:
1. Insert key in the ignition and turn the switch from OFF to RUN (as far as you can go without cranking the engine) eight times within ten seconds, ending in OFF.
2. Doors will lock and then unlock, verifying a keyless entry system is installed.
Mind FAILED this test! I must try again in daylight; it is actually kind of difficult to do within ten seconds.
KeylessRide's price is $29, plus $20 shipping to Canada.
I see some for $15 and under on ebay, with another $15 charge to mail to Canada.
It is just a little much when I'm not certain it will work.