Need Help on Fluid choice

I have an 833 in my Dart. Well built 340 and aggressive driver :p I've been running the Sta-Lube 85W90 hypoid gear oil in mine. When I just went to purchase more , it looks like it has been discontinued.
1) Am I wrong that it's been discontinued?
2) If so , what is a good equivalent oil to run in there or the proper fluid ? Was that even a good fluid to run in it?
Thank you in advance.