In mid 64, the firewall was changed on the A body to accommodate the V8. An integrated AC/heater assembly was then offered for the first time.

Will this assembly bolt-up to the 63 firewall? Do any modifications need to me made?

TIA

--Walt Jackson

Your chronology actually isn't correct.

The firewall change occured with the changeover from model year '63 to model year '64, not in midyear '64, though the V8 was not offered until midyear '64. All '64s have the "after" firewall and wiper motor mount; all '63s have the one-year-only "before" firewall and wiper motor mount.

The integrated heater/AC was not offered until late in the 1965 model year, not anytime in 1964, and there were box changes and differences across the time period this general system was in use (late '65 through '72). There are a great many pre-dimpled holes and such in the late-'65-and-newer firewalls that are not present in earlier firewalls, and even the later ones do NOT have ready/easy provisions for adding the heater/AC unit -- the dimples were not intended to make it easy for aftermarket installation of the system, they were there as final guides for factory punches and such.

Having done this conversion on a late-production '65 that had all the dimples and stuff, I can tell you it is a MAJOR pain in the rear. You need to convert from rod to cable throttle (accelerator pedal, cable, brackets, trans linkage, and plenty of drilling/cutting), run new vacuum lines and wires, etc. Also, the early (up to '67 or so) variant of this system has a weak defogger and weak A/C performance. The later units (especially '70-'72) are better in both regards, but especially with today's less efficient R134a refrigerant, upgrades would be highly desireable especially to the condenser.

I do favor original-type upgrades. I would rather see a genuine/more-or-less-correct Chrysler A/C system in a car than a modern system from one of the hot rod A/C vendors. But know in advance, it is not a simple or easy thing to do.

And to answer your direct question (finally!) No, this system most likely won't bolt directly to the '63 firewall. The wiper motor and its mount are in the way, there are bends and fittings that interfere, etc.