Good luck with the sale. Glaval made nice units. That is a very nice '93. hope you get the 5K for that well preserved Chevy. 350 is a plus.
The only thing I noticed while towing 5,000 lbs with this GM transmission in my 97 pickup with the same drivetrain is that it sucked towing in OD, hunting down and not maintaing 4th, high gear, and if you downshifted to D you were in 3rd and winding out to maintain hwy speeds. My solution was low buck and looked funny as

To prevent the downshift under load in OD, what I did was mount up a smaller diameter tire, a M-S, and load rated SUV passenger type tire on the rear that allowed the truck to be much more easily able to remain in OD, and tow on the flat without driving me nut's.
Underneath, from NH, hope it doesn't look like it's from Ohio.

Van on! G'day!