The first cut is the deepest

The oil needs to travel from the adapter to the oil filter, behind the firewall. A hole in the fire wall is a first step. (A lick of rust protective primer hopefully prevents rust on the cut line). To make this mess a whole neater, another aluminium cover, painted in black wrinkle finish, equipped with proper rubber grommets to protect the oil lines was fabricated. M6 Captive nuts allow for a neat installation of the cover: