Mate buying a couple of cylinders and dropping them in isn't going to fix what sounds like a massive job. You'll be up for piston and rings, cylinder re-lining or even two new cylinders, the heads are most likely hammered as the crank and connecting Rods would be, and you'd be lucky if that was the least damage. When things let go inside try tend to take down everything with them.
I'd suggest taking it into a shop for an inspection as I don't think you quite know what you're looking at, but unfortunately it is going to be expensive and probably out of your hands. However it is doable yourself if you dedicate time to learn! Good luck...