IIRC the firewall is dimpled where the cannister bolts. It's just a matter of locating those and drilling them. I believe it mounts with hex head screws with a 5/16 diameter and is also slotted.

Have you decided where you are going to run the vacuum hoses. There are 2 locations used. One is next to the regulator and the other is above the heater hoses which seems to make more sense. it is rather crowded when placed by the regulator.