if the engine you plan on using is a non roller cam use 75-84 duraspark
distributor with a factory cast iron gear and if its a roller cam use
1985 only carbed distributor with the factory steel gear,as for
ignition use msd 6a or 6al ,you can also use any coil but 4,6,8 efi
coils are good. also do not use a bronze/brass distributor gear unless
its a dedicated race car.

much easier and save lots of time and money to buy a 5.0 intact, for $2k,
and dump the 79.
at least all the parts will match up.

It's good to see you want to put some effort into a project.  Nothing
wrong with that at all.  If I were starting from scratch and building a
Mustang I would use a 351W motor.  It will fit into the Fox Chassis and
it has far more potential, and the block is stronger, than a 302.  Plus,
most of the parts like heads etc. that fit on a 302 will work on a 351W.
 You can even use the stock hood if you use engine mounts that lower
the engine in the bay.  They are available.

As for brakes, check out this site:  http://svo73mm.cjb.net/  The
information on it applies to a '79 also.  You might want to print the
information on the page because it is old and might disappear one day.
I have used information from it on my own Mustang.

Almost all the parts of the Fox chassis models are interchangeable.  I
have seen guys install the nose pieces, dashes, interior trim etc. into
the earlier models.  It takes work but anything is possible.  One thing
to do is install subframe connectors.  They will stiffen the chassis a
great deal and would be a good starting point to keep it rigid while
working on the car.  You can buy them or make them.  Mine were
fabricated by a speed shop and work great.  Also, weld them in.  Do not
bolt them on as this makes them far less effective.  There are many
other things to mention but I don't want to write a novel here.

My advice is to do plenty of research.  The web is a great place to get
ideas and nail down what you want.  Having a detailed plan BEFORE YOU
START will save you a lot of money and aggravation down the road.

One last thing, if you are going to frequently visit here, or elsewhere
on the web, grow some thicker skin.  Opinions, on Usenet especially, are
like elbows and a$$holes, everybody has them.  Some people expresses
them gently and some like to beat you over the head with them.  Don't
let the latter bother you too much.  It just isn't worth the self
inflicted agony.

So, are you saying Ford engineering and building abilities are inferior to
your own?  How many cars have you designed, built & sold?

Having modified and bastardized damn near every aspect of a car that could
be done, I offer my very sincere, experienced point of view with you best
interest in mind, not mine.
Many decades ago, when I was 16 and asked this "old" middle aged coworker
whom had converted a automatic car to a manual transmission car for his
assistance on my project doing the same, his response was quite frustrating
to me.
He said No he would NOT help me with the project, and that if I wanted a
manual transmission car, I should buy a manual transmission car. (Keep in
mind, they DID NOT sell kits for such things back then).  I was upset and
somewhat insulted by his reply and advise.  I did that project, and
eventually a second one too, and eventually learned, what he was trying to
tell me in the first place, in retrospect, he was dead nuts on with his
advise.

If you want a  V-8 Mustang, buy one that came from the factory that way.

The acronym KISS really does apply here.  The vast majority of backyard
engineering can't hold a candle to Fords engineering.

Yes you could put an engine together, just how you want it, but why do that
with an old body that will then need all new cooling system, suspension,
transmission, rearend, fuel system (?), wheels, brakes, engine stands &
mounts, exhaust system, etc, when you could simply build an engine to your
liking, and put it right into a complete fully functional factory V-8 car?

Here is a prime example of what all of your blood, sweat and tears will
amount to in the end, a highly bastardized car that isn't worth what the
original unmolested one was.
http://ebay.com  Item number: 200049442135
http://cgi.ebay.com/ebaymotors/1985-mustang-convertable-with-1991-front-end-1999
-cobra_W0QQitemZ200049442135QQihZ010QQcategoryZ6236QQrdZ1QQcmdZViewItem

I prefer to enjoy driving my cars/trucks, not chasing my tail attempting to
reinvent the wheel.
I have turned wrenches for a living for way too many years, I like many
people, don't derive much pleasure from doing it in my off time.
If you would prefer to avoid reality & continue living in your bubble, have
at it and good luck.

Besides, your analogy is a little off, working your a.s off, saving your
hard earned money and buying the car you want is not having it given to
you...