x2 on it being bad. Keep us up to date on your search. Rebuilding an engine would be a good winter project.

 

I managed to do similar damage to all the driver's side pistons on my Chevelle when convering it to tuned port injection. I did not open holes to the crankcase, but the ring lands were damaged enough to drop the compression from 150 psi down to 50 psi. Best I can figure, I had a lean condition leading to preignition. I was still able to drive it, but it ran like s...

Go with a JY engine out of a wrecked cherokee

 

With the motor out of the Grand you will need to use the accessory brackets off of your motor and possibly the intake but most everything else will swap over.