700 king quad rebuild or replace engine?

[Bwdeaton 10]

I recently picked up a king quad 700 that doesn't run in the hopes of getting it running by spring. It had been previously taken apart some and a few pieces are missing in the engine, but the frame is complete and in good condition. The motor will need a piston, rings, cylinder, cams, and a few misc parts that are missing. Also the cases will need to be split to remove the pieces of piston that are in the crankcase. The piston blew up at high rpm and did a number on the cylinder so I'm trying to find out if it would be worth rebuilding this motor it buying another engine to swap in. There may be more damage to this engine that I can see so I was wondering how bad the insides of it could be considering it destroyed the piston. I have found a motor for 1200 plus 200 shipping, the only problem is I don't have that much now and I would have to save up a while before being able to afford it. Any suggestions appreciated.