Sucks to hear Mike, don't give up now. There's still time.
I know this don't help you, but years ago I had a sb 727 that least 3 local shops worked on and it was never right.
I helped my old boss rebuilt a 727 out of his work van one time, long time ago. And I got good at building shorty powerglides for my early dragsters, but I wasn't gonna try to fix that old 727 after so many people worked on it. I got some of my parts from Coan Trans in Ind for my powerglides(I built 4 of them, one for a buddy) and raced with him and his son when we raced super quick.
So I called them and it was 600 bucks and a core for street fighter sb 727. I took them the 727 nobody could get right and swapped for there trans and is the best I ever drove. Crisp shifts big time and still today over 14 years later. Then I bought a second 727 for my 440 a few years later and I think it went up to 650? this was in 2005 when I built my gold challenger. It still rocks today 10 years later, kills the tires on the shifts, love em.
All these years later they have been great values.
I also used there custom converter too, it was not big bucks at all, they were cheap compared to a 8-9" racing convertor.
Good luck with whatever you decide.