Being a turbo DSM, my car has an iron block but an Aluminium head. Several of the holes on the head have actually stripped out, my Exhaust manifold is currently held on by 7 bolts instead of 9 because two of the holes stripped out during my last turbo swap, and one of the spark plugs isn't threading correctly due to scoring inside the spark plug tunnel. I want to rebuild the head and sell it after I pull out the engine, but it's pretty much useless in its current state. Does anyone have any tricks to restore the threads in Aluminium blocks without having to re-bore the whole thing?

yeah, you're probably gonna have to drill and thread the old holes

You can't start out with smooth bore holes for this, but try heli-coils with a dab of high temp epoxy. I would just advise heli-coils, but with you're aluminum head, you want to make sure it stays and doesn't walk around in the hole. That would cause it to wear out the remaining threads that the heli-coil grabs onto. Either way, Good luck!

If you do heli-coil MAKE sure you do it PERFECT the first time. Obviously you only have one time. The heli-coils can work for those applications, just to make sure you use the correct drill bit and a BRAND new one with a new tap(much nicer holes) DO not force the tap, go forwards a turn and then back up a couple, then proceed to do so untill finished. Use some lubricating oil to make cleaner cuts.
Then when you are done, make sure to use a high temp thread locker.

If all else fails, EBAY!!