Thermostat Housings... What's the difference?

[itchyfishnv]

Can someone tell me what the difference is between a pre-1999 and post 1999 thermostat housing for a merc 3.0? Other than the 90 degree inlet for the transom hose, I'm not sure what the difference is. They use the same gasket and mounting. I purchased a new base 3.0 engine and curious if I could use my existing t-stat housing from my 1987 3.0 since its only a 2 months old.