Nothing, no difference but the connectors.
Same with the packs.
The 86 doesn't fit the 87 as they used the screwdown connectors.
The 87 and up used the screwdown connector and the early 86 and before used the plug and play.
The screwdown connectors: they have a problem with the wire, it breaks easily under the shrinkwrap.
I replace them as SOP when I work on the trigger.
Actually I replace ALL the connectors.