Get the specifications for the
front track width of both vehicles. If it is identical. Then, your assumption could be a
maybe possible fit from strut tower to strut tower.
Bear in mind that although the strut brace might line up on your Avalon...the brace bar may interfere with engine components. Like the master cylinder etc. I ran into this problem trying to fit an 06 Matrix XR TRD brace onto an 09 Matrix S. And the mounting lined up but the Brake master cylinder was in the way. I ended up ordering the 09 XRS OE brace instead. It was shaped appropriate.
Have yu checked to see if the 3rd gen Avalon
"Touring" edition gets the strut tower brace?? It is the Performance Handling version of your model. Yu might know this already?
I doubt there will be any aftermarket support for the Avalon.
LT