dont attempt to do it your self talk to local shops and find someone that can weld alunimum, a replacement cavitation plate is less then 100.00 and you should be able to get it welded for less then 100.00....it realy should be tig welded then you dont have to gut the drive
or you can do it, boil the drive lube, blow out the seals run till it stops and call one of use so we can charge you 2500+ to rebuild it when we really dont have the time to
its up to you !!!!
Im not trying to be mean just trying to get a point across, its all good