Engine question

[DR SCHNITZEL]

My front rotor has gone:eek . what problems are there in finding a cheap engine with a rear rotor gone then using a rebuild kit and making a good engine from the 2. i know i will need new housings and plates as i drove the car 40 miles once the thing had blown and is showing almost 0 compression on all chambers. im just trying to do a quality job as cheap as possible. i know those two words dont work well togther.:spank
 
My initial thought is if the rotors in the 2 engines weighed substantially different then the lump would not be balanced. any thoughts?:2Rolleyes