Here is some good info on the engine nos. for all mitsu engines and what all the nos and letters mean.

http://www.answers.com/main/ntquery;jsessionid=7lahvpcikiorv?method=4&dsid=2222&dekey=List+of+Mitsubishi+engines&gwp=8&curtab=2222_1&sbid=lc05a&linktext=List%20of%20Mitsubishi%20engines