Not sure if I’ve ever seen a template that somebody made and put out there.
Wouldn’t be hard to do, but only if someone’s got theirs out laying around. The problem with that is that, most of the old ones that were fiberous just tear to shreds when you try to pull them off the firewall.
The modern replacements that are all polyethylene-backed and firm, are out there. But they’re expensive.
Hopefully someone’s got a bare firewall or a mat that’s laying around to work with you on.
Or you could just make your own by laying the material of your choice up on the firewall. Forget how Ford did it. Do one best for you! I like the brand “quality heat shield“ which is a really nice aluminum back and flexible material that’s mildew resistant and very good insulator.
Or you could do what many do, and just put one of the adhesive backed materials similar to dyna mat on the firewall.