Methodology rather than where to put it...
When I built my -8 I was in a real quandary as to where to put things so as not to interfere with other "stuff" like engine mounts, oil filter, mags and other things to come later.
Once I had my engine, it made it a lot easier to visualize where the "spaces" were. I temporarily mounted the engine mount onto the firewall, then would move in the engine on the engine hoist to try and determine where the "fixed" items would go, thus identifying the "spaces" that could be used for stuff that was less critical.
Once I had finalized locations, I mounted the engine mount to the engine, but kept it on the hoist to move it in from time to time to confirm clearances while I worked on wiring, plumbing etc...
By the way, my air-oil separator is mounted on the upper right of the firewall but it is homebuilt rather than ASA... This may or may not work for a -10...
Sorry, I tried to post a couple of pictures but unfortunately Photoshop seems to have a glitch today and I can't seem to pick up a copy... I'll try later...