Shaft seal replacement

Ah, yes; I made a tool similar to that, many decades ago.
But I have never tried to do the job you described,
Mostly cuz;
my personal record for taking my all-aluminum A833 down, is 17 minutes.
That includes dropping the 3" dual exhaust, the driveshaft, the shifter;
splitting off the GVod, blocking up the engine, and dropping the crossmember, etc.
That does not include draining it.
This was done on a 4-post lift, with all the required tools already on the tool cart.
This was the third time that week, and so, with the practice, it was the quickest. I had tried it, the first time, with the GVod still attached, but with the extra weight, and awkwardness, that required a helper. Whereas, by comparison, the all-alloy box by itself, I could take down by myself. IIRC that box is around 85 pounds, plus oil?
Oh to be young again.

Why you ask?
Well, I was gung-ho to make synthetic oil shift faster than DextronII. After three unsuccessful attempts, I took the trans down one more time, and washed all that chit out.
With all the changes I had made, the trans, now with a 50/50 recipe of Dextron to EP oil, shifted like greased lightning. It has Not been down since.