You would have to take the output shaft in the 89 smallblock trans 727 and install it in your big block 727 case and put the 241 adapter housing on it thats what I did on my 77 Ramcharger with a factory 440/727/203 setup that I converted to a 1984 727/241 part time transfer case setup and I had to change driveshaft lengths at least on the rear.

An issue you might run into is when swapping the output shaft you need to make sure the year big block trans is I believe 1976 and newer (I thought I read somewhere the years were 76-93 had the same spline angle) since they changed the angle of the spines on the output shaft and if you mismatch the parts its a good chance they could strip out.