4ksq clutch replacement

[Dave Fain <KC3565L@sprintmail.com>]

Can anybody tell me for sure if the clutch and pressure plate
in my 1985 4000S Quattro are essentially the same units used
in the VW Fox?  Even the counter guy at the auto supply place
was surprised at the price of the throwout bearing and pilot
bearing for the Quattro so I wonder if the price for the same part 
doesn't magically go up when you say "Audi".  Please correct me if
I am wrong, but the 5 cylinder Audi engine looks an awful
lot like the 4 cylinder in my 1989 Fox with an extra
cylinder grafted onto the front of it.  I have heard that
a 4000S (non-Quattro) transaxle will fit a Fox, is this correct?
How about the water pump?  Are they interchangeable?
Thanks, Dave