changing alpha one gen 2 to bravo 3 ?

[diehard]

i am sure this has discussed before but did a search in the archives and could not find any info on it ..i want to changing my alpha one gen two out drive to a bravo 3 out drive ...i know i have to change the out side transom/gimbal assembly do i have to change the assembly / bell housing on the inside of the boat ? will i have to modify the hole in the boat where the out drive goes threw ? if anyone could me find some info or post a link on this i would be a happy boater ...thanks for reading my post have a happy 4th