The Challenger stocks were Beech, mine is but luckily highly figured, I have another challenger stock that is bland as hell, the Lightning barrel and breech block will just swap straight over, the only problem you may encounter is the slot in the bottom of the breech block where the cocking lever pins into can be a different size sometime and may either need a small washer in there to pack it out or may need the links closing up, the barrel pivot pins are the same size whether it is the bolt or pin, the Lightning is basically just a a Supersport with a shorter barrel and silencer and a Maxigrip scope rail.
I've never handled a Cobra strike or any older .25 barreled BSA's, I've only ever had .177/.22 Mercs or Challengers, the older .25's have really tight barrels as they are .243.
Pete