Colin's right as always, the ignition switch on 1986 cars was standard BLMC, when mine went I replaced it with one from an MGB as I could get one easily. If you don't want to wait for Uncle Melvyn you could probably get one from the MGOC.
I found no problem getting my old shear bolts out with a punch, when I fitted the new one I left the heads on the shear bolts, I couldn't really see any point in breaking them off.
You might find a difference in the plug connectors, they went from a more square to a rounded one (or the other way round, cant remember) not an insurmountable problem but they are not directly compatible, Tandy and others sell plugs sockets and pins to overcome this.
