help quick! question about 40hp lower unit

My husband has a 40hp motor that needs a new lower unit. my question is, are the 40hp lower units all pretty much universal? As in, would it be able to be used on a 4 stroke 4 cyl, if it came off of a 2 stroke 3 cyl? Also would it work on a 99 if it is from a 2000? I need to find this out as soon as possible....my husband's Christmas gift depends on it! Thanks!

[boats.net]

1995-2006 40 2 stroke will work, the 40 four stroke lower unit is not listed to interchange with 2 stroke models.