Not sure if I should just start a new thread at this point, but here's the history to the best of my recollection:

- This is a 1985 GT 5.0 convertible, completely stock except for my Dynomax exhaust. It has the factory Holley 4180c carb on it. No codes to pull.
- Between my dad and I, we've owned the car since new in 1985. So there's no funny business with botched work (unless I did it).

- It's always been a FL car, but 2014-2017 I was living in CT for school with the Mustang in storage. It got driven occasionally when the weather was nice.
- I could tell the intake gaskets were very slowly leaking in the back by the time we graduated residency in summer 2017, there was residue back there, but when warmed up, no leak.
- We drove it from CT down to FL with my now wife back in July of 2017 when we relocated to FL -- not an issue with cooling or anything that entire 7 day trip (same as it has been since 1985)

- I drove it to work occasionally that summer, but it started leaving a large puddle under the car from the intake gaskets
- I stopped driving it, and started replacing the intake gaskets Oct 2017
- I had the car apart for a while (new job, life is busy) and got the intake gaskets done a month later at the end of Nov '17
- Decided to replace coolant, this is when the Freezetone/Prestone 50/50 mix went in.
- Started car, set timing, adjusted carb, etc after having everything off for the intake gaskets - drove it around the block only and let it heat up to make sure things were good with the coolant level

- Decided to replace the inlet heater hose, because when I took it off to remove the intake, it was pretty swollen.
- Knew there was a high risk getting it off the heater core, but did it anyway and the core developed a big leak (ugh)
- Replaced heater core (Motorcraft) and hose (Napa), and added restrictor bought from Ford and placed in heater inlet hose right after the intake ~Dec '17
- Filled coolant back with recovered Freezetone/Prestone and checked for bleeding and warm up.
- This is when the overflowing issues started
- Decided to drive car to work one day now that it was "reliable" again, and halfway on my 15 minute drive, I see the temp climb way up the gauge. I limp the last few miles to work coasting and starting and coasting and starting
- I can't remember if it overflowed when I got to work, but I went home to swap cars at lunch and it definitely overflowed and overheated (and that was just about 6 miles home)

- That's when I started this thread Jan 2, 2018. In fact, my original post clears up some of the details to me now - it originally overflowed driving on the highway, which I probably didn't notice until driving to work the next day

So since Jan '18 I have:

- Replaced thermostat and housing (Ford Racing housing and Motorcraft t-stat)
- Replaced radiator cap (carquest)
- Placed spring in lower hose (NPD)
- Had radiator "rodded" out (local shop here in Tampa)
- Replaced radiator cap again (Stant)
- Replaced water pump (Airtex AW4024)
- Replaced fan clutch (Napa)

Every time no matter what is replaced, the story is still the same. Fine around town, fine on the highway for a bit (then I see the needle sit a little higher after a while -- from the middle of "R" to between "R" and "M"), and then it overflows/boils over when I get off the highway.