Based on recommendations of other builders, and common sense, I pre-ordered the oil cooler mount from Van's and I'm installing it now -prior to the firewall forward kit. Assembly was quite straightforward. The only challenge was dimpling and the subsequent riveting of the two rivets which are blocked by the air intake. I used a combination of close quarters dimpling tool and just hammering a rivet with a flush set and a countersunk piece of steel. Came out good enough.

Back-riveted everything to the firewall. The two tricky rivets used a thin steel bar backed up with my tungsten bar to back-rivet. Again, good enough.

Sealed the holes and around all of the edges with 3M fire-resistant caulk to make it air tight.