Sorry, it is 536. From exit 6, take 536 right to Disney.
You can go online and buy a SunPass windshield sticker for $4.95 and they will send it to you (even when you aren't lucky enough to live in the Sunshine state)--www.sunpass.com. You can cancel the account after you have finished being a Florida tourist, or you can keep it and come back again! No monthly service charge. At some point all these toll passes are supposed to work together, but not yet. Considering just the gas for the trip (and not the cost of Ft Wilderness and Disney tickets) $4.95 plus the same in tolls is better than waiting to pay at a tollbooth or waiting (and waiting, and waiting) in construction zone infested I-4 around Orlando. Just a thought...