Fleet vehicles was one way for them to buy the cars they want option wise plus they would get a discount that way too,they have to buy a certain amount of cars. It still happens today
I think you might be on the right path with gaskets being bad.
But chasing down problems like this are a pain in the ass.
I’ve been playing with foxbodys since “91” and had my last one for almost 11 years now and it still surprises me with strange problems time to time.
I have read this thread...
Long time mustang owner but new here.
I have had similar problems in the past and the fix for me was simple.
First thing to try is after you shut it off, try some starting fluid and see if it starts.
If it does then you most likely have a tps going bad and it will get worse before it totally...