I quick hunt on the internet provided me results.
Looks like this grade A american did exacting what i want to do.
1.Trimmed it back to the firewall from the outside
(im very good at cutting things, you guys should know this by now)
2. Trimmed a path for the air to get to the blower motor, and then covered the cuts in bubble gum.
3. Cut out a a piece of metal and blocked it off from the outside.
Id like to do the same exact thing, except id like my template to look a bit more "refined." Maybe even let Jersey Mike spend 34 man hours polishing it