Would anyone know if a 1.00 a/r exhaust wheel can be used in a 1.15 a/r housing?

 

Exhaust turbine wheels don't have a/r associated with them. Their size is measures in "trim". The only thing that gave your old turbo a 1.0 a/r exhaust was the old 1.0 housing. To answer your question, yes, you can change just the exhaust housing on a turbo.

 

Understood. Thanks !