Automatic trans needed '87 4000S

[Dave]

I have been absent from the list for a while so be patient if 
I ask questions that were recently answered.  I just got a deal 
I couldn't refuse on a 1987 4000S (not Quattro) with a fried 
automatic transmission.  The car is otherwise very clean and 
original and too nice to part out.  I am looking for a replacement 
transmission at a reasonable price within an hour or two's 
drive of Denver.  I know the drive train is similar to the 
VW Jetta and Fox.  Will an automatic from one of those cars 
fit the 4000S with no mods?  Is it worth the trouble to try 
to convert it to a 5 speed?  I might be able to salvage the 
clutch and shift linkage from my recently deceased '85 
Quattro.
Thanks,
Dave
1990 90Q 20V
1987 4000S