After some research I came to find out that Ford offers revised Ignition switch for 87-91 F series/Bronco.
I replaced the ignition switch with hope to resolve "hard to or not starting when warm" problem on 87 F150, didn't resolve the problem but nice to have improved switch installed. Original design is known to cause connection problem and in some cases fire, some articles can be pulled up from search engines under "Ford ignition switch".
Dealers will try to sell you original old design if you don't ask for the right part number. Ask for SW-2472 or F2TZ-11572-E, actual part came in the box was stamped F2TA11572EA This means it's Revision EA. Original switch came on my truck reads E7TA-11572-AA this means it's Revision AA(the old skool original faulty design!).
Advanced auto parts wanted almost $12 for aftermarket unit, dealer wanted $16.60 for original faulty design switch and only $13.28(list price) for revised SW-2472. I called around for this part number and some dealers knew and some didn't know about design change. I bought mine from Burd Ford in Indianapols, didn't have one in stock but got one for me in an hour even on Saturday!.

 

Our shop buys ignition locks for Auto Security Products (ASP) 87 used a 10 cut key which is needed to remove old lock to replace with a new lock.
I imagine you are talking about the switch bolted to the column that the pushrod engages to start the engine. I replaced mine with one from AutoZone - worked fine.

 

yes, this is Ignition switch. not the Key cylinder.