Bummer
I never expected the flanges to be different either I guess. I wasn't saying it was your fault. I wonder if maybe that's a Chevy rear. That's the only reason I can see that it would not work. Dana's are tough to work on. I think Chevy used that rear too. I wonder if you can identify that what that rear is and get the disc setup for that. Just a thought. Does the new rear have the axles in it? If so, make sure the wheels fit.

You're right about the ratios though. . . .I share your pain and understand