On an Aspen project that I am working on, I went from power to manual. I had to use and aftermarket rod from Summit. Had to cut the rod way shorter than what it was designed. It now fits with less than 1/2' pull out on the pedal. Still on the stands. Have not tried brakes or pedal. I'm thinking this might be an easy answer.

On my 71 Demon I did not have one of those rubber bushing so I filled the cavity in the master cylinder with a Black RTV and placed the pushrod in it over night. I used that for about a year or so, one morning backing the car out of the garage I went to step on the brake and the pushrod had fell out. Car did not go anywhere that day and counted it as a blessing it did not happen at the track.

I called the Doctor on the next Monday and ordered a few of those rubber bushing. Still got one left.

Just remember the rubber bushing doesn’t address the issue

Has any one heard of the rod coming out with a stock OEM retainer?
I haven't and removing the rod when replacing the M.C. is a real pain with a lot of effort required
I had to cut one piston in half on one M.C. to get the dang rod out

The stock style bushing can be used, once. It should not be reused if the assembly has to come apart. I would still use some sort of mechanical stop on the pedal. And verify the assembly of the pushrod to brake pedal hardware.

I pulled the rod out of the master a couple of times when
they were new.. was still a PITA but once they are older
you can forget that.. it shears the rubber off.. on my
set up I used a .120 OD push rod with the end welded on
and being smooth I couldnt use the stock type ring so I
added the perminate stop and never had any issue

Happened to me on the Major Degan 50 years ago, new GTX, managed to get the car stopped despite heavy traffic.
It was called the "Jesus pin" for both what you say when you discover it, and who the next person is that you see if you're not lucky.

I had a major break failure yesterday... the
pedal went a bit farther than normal.. I hit the
pedal again and it went to the floor.. I was on
my way home from CVS so I took the back road.. I
made one turn and there is a car in the ditch so
I stopped to help.. got her pulled out and made it
another mile to make it home.. I will fix it when
I return from vacation