IMHO: Even a standard 60-75 two stroke engine installation requires an extensive hack job on the cowl to make it fit that cowl.
The plane is set up to use an upright mount engine, that in a pinch could be mounted upside down.
With your larger engine you are looking at cutting even more of the cowl away and you'll have problems getting the cowl on and off without large cutouts.
Consider not using the cowl at all.
In your shoes I'd be attempting an inverted engine mount instead which would leave the muffler hanging down and back preventing oil from getting onto the plane.
This would also make it easier to get the cowl on and off with one opening on the bottom, and will be less unsightly.
This kind of thing is not really for the novice though.
Some will tell you that running engines inverted is problematic.
Don't listen to that nonsense, they merely don't know how to tune their engines properly.
You may have to spend a bit more time making sure that you have the engine tuned up and you should run the engine uncowled until you have the plane flying reliably for your own ease.