This morning, /u/Smitty_Oom posted this 2018 article in /r/cars, A Brief History of the Ford Probe, and it hit on many of the points I made in my post last week. The post generated quite a few interesting comments, in particular was a comment made by /u/r_golan_trevize who helped fill-in some of the blanks on Ford’s decision making on the Probe, Mustang, and Thunderbird.

From the thread:

The MX6/Probe… debacle isn’t quite the right word… anyway, whatever you want to call that period in Ford’s sport coupe development history is an interesting one with ramifications that were felt well into the 2000s.

All Ford’s chips were in on the Probestang so when they got hit with all the backlash (Ford execs got death threats about switching the Mustang away from a RWD V8 layout) there was no money to develop another next generation Mustang so the Foxbody had to soldier on for another few years unchanged with mainly aero composite headlights and a ground effects body kit to distract people while they could work on a new RWD Mustang – and it worked as the ’87-’93 Mustangs were very popular.

At the same time, Ford was working on the new MN12 Thunderbird/Cougar platform which would debut in 1989. This was a completely modern RWD personal luxury sports coupe platform with a fancy IRS and designed to take Ford’s new modern Mod motor V8s and designed to take on the Germans. Ford put a lot of effort into the MN12 project and when the need for a modern RWD Mustang arose, they would have liked to have put it on a cut down version of the MN12 but unfortunately, development costs had spiraled out of control and made the MN12 too expensive to use for the low cost Mustang.

By the time Ford really had to get working on a new Mustang, there was no money left between the Probe and MN12 projects to engineer an all new one so they had to pull a rabbit out of the hat and rework the old Fox chassis (already dating back 16 years now at this point to the 1978 Fairmont) as best they could with no budget, rebody it and squeeze another 10 years out of it (and that’s how essentially a 1978 Fairmont ended up in the 21st century with a 400hp supercharged 32V V8).

With this additional information, I would add the third (1979-93) and fourth generation (1994-2004) Mustangs and the Ford Thunderbird/Mercury Cougar (1988-1997, MN12 platform) to Ty’s list.