That really depends on the type of mount on the RV6 now.

If the mount pads are tilted inward, and the pads on the O360 are machined at an angle, this is the most common and it should work.
 
Your engine has the Dynafocal 1 engine mount configuration.
So you are looking for a parallel valve 180 hp with Dynafocal 1 engine mount configuration.

Good luck