Now that we're in the paint phase with the engine compartment, the 
whole automatic choke question has to be dealt with.  Bill and Bobby (1st and 2nd owners, respectively)
both have stated vehemently that the car had an automatic choke (and no 
choke pull inside the car) when they each purchased the car.  In fact, 
the way that the "L" bracket is welded between the side of the cowl area
 to the dash, the holes for the choke pull bracket can't be mounted 
where it is supposed to go - the mounting holes in the bracket are 
blocked off by the holes in the bottom of the dash, due to misalignment -
 the tab on the choke bracket and the mounting screw won't fit through 
the holes. 

 That said, the car did have a manual choke when I acquired it, and Jay 
stated that as he and his son recalled, it had the manual choke cable 
when he painted the car in 1980.  Jay's recollection is that it was also
 there in 1973 when he first acquired the car.  The choke cable on the car when I bought it was only 46" long and the exterior covering was thinner and 
lacks the white line I have seen on other originals of the production 
period for this car (Fairlane was 58" long vs. the normal Mustang HiPo 
length of 63").  When I acquired the car, the pull was mounted in the 
"D" hole under the dash and the cable was routed in front of the fresh 
air vent inlet housing under the dash, rather than behind the fresh air 
vent as it was supposed to be.
The
 hole in the firewall is very crudely made, it was apparently drilled 
through first, then punched through with a rod from the firewall side, 
which splayed out the metal on the interior side of the firewall.  The 
metal that remained around the hole was then pounded flat against the 
firewall.  The area around the hole is dented by about a half inch 
towards the drivers side by hammering of the punch through the firewall 
and/or the prying action of the metal rod.
So the 
question is, "when was this hole made?"  Was this done at the factory or
 during the time between 1970 (when Bobby bought it with an automatic 
choke) and 1973 (when Jay bought it with a manual choke).  One wouldn't 
expect such a crudely made hole to be done as part of normal assembly 
procedures, but there are several other holes in the area around the dual exhaust that were all hand-cut, some very crudely.  So it's entirely possible, that the existing hole in the firewall was made with the intent of installing a manual choke later in the assembly process.  But, based upon the way that the hole was made and plugged it is very unlikely that this was a factory made hole.
One factor, is that it looks like the hole was made with the 
firewall pad in place.  The "chad" that originally covered the hole in 
the firewall pad was still hanging off the hole and will be reused with 
the original firewall pad in the restoration.
The other factor is that the assembly instructions called for any penetration of the
 firewall to 
be sprayed with sealer after the items penetrating the firewall were 
installed as one of the last steps before leaving the factory.  the sealer is often sprayed haphazardly, this is no exception.  There is sealer over-spray in the area where the cable goes through the firewall. 
 The plug of caulk that was used to seal this hole was 
applied over the spray on sealer, indicating that the hole was most likely made and 
caulked after leaving the factory. 
With all of the evidence some restorers would go ahead and weld the hole closed.  In this case, however,  I am not going to do that.  I learned over the years that the best approach is one that leaves the most original evidence, so that if more info comes to light in the future,  we still have the ability to again review the original evidence against the new information. 
This proved especially true of the lowest VIN coupe, 5F07U100002, that i sought out and bought in the 1990s, and subsequently sold to Bob Fria.  Had I chosen to restore that car using the prevailing knowledge at that time, much of what we learned about pre-production Mustangs would have been lost.
So I'm staying true to the statement in my introductory post, that this is a "minimalist restoration".  Therefore, the existing hole will be covered with body sealer that could be removed in the future without destroying historical evidence.  This is consistent with what the factory would have done if such a hole had been made at the factory and not used.
Just one more comment on what i mean by "minimalist restoration".  We are still doing a complete, down to bare metal, rotisserie restoration.  However, we have preserved every existing original marking and part that we could, and we documented in photos and accurately recreated those that could not be preserved without compromising the structural integrity of the car, its appearance, or durability of the restoration.